Glossary

Numbers in brackets refer to the chapter(s), Appendix (App), or A Step Further (ASF) where the term is introduced.

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5-alpha-reductase
An enzyme that converts testosterone into dihydrotestosterone. [8]
5-HT
See serotonin. [4]
17-beta-estradiol
See estradiol. [8]

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A

A delta (Aδ) fiber
A moderately large, myelinated, and therefore fast-conducting, axon, usually transmitting pain information. Compare C fiber. [5]
absence attack
See petit mal seizure. [3]
absolute refractory phase
A brief period of complete insensitivity to stimuli. Compare relative refractory phase. [3]
accommodation
The process by which the ciliary muscles adjust the lens to focus a sharp image on the retina. [7]
acetylcholine (ACh)
A neurotransmitter that is produced and released by the autonomic nervous system, by motoneurons, and by neurons throughout the brain. See Figure 4.3; Table 4.1. [3–5]
acetylcholinesterase (AChE)
An enzyme that inactivates the transmitter acetylcholine. [3, ASF 4.1]
ACh
See acetylcholine. [3–5]
AChE
See acetylcholinesterase. [3, ASF 4.1]
acid
See LSD. [4]
act
Complex behavior, as distinct from a simple movement. [5]
ACTH
See adrenocorticotropic hormone. [ASF 8.3]
action potential
Also called spike. A rapid reversal of the membrane potential that momentarily makes the inside of the membrane positive with respect to the outside. See Figures 3.6, 3.7. [3]
activational effect
A temporary change in behavior resulting from the administration of a hormone to an adult animal. Compare organizational effect. [8]
acupuncture
The insertion of needles at designated points on the skin to alleviate pain or neurological malfunction. [5]
adaptation
1. See sensory adaptation. [5] 2. In the context of evolution, a trait that increases the probability that an individual will leave offspring in subsequent generations.
ADH
See antidiuretic hormone. [8, 9]
ADHD
See attention deficit hyperactivity disorder. [14, ASF 13.4]
adipose tissue
Commonly called fat tissue. Tissue made up of fat cells. [9]
adrenal cortex
The steroid-secreting outer rind of the adrenal gland. See Figure 8.1. Compare adrenal medulla. [11]
adrenal gland
An endocrine gland atop the kidney. See Figure 8.1.
adrenal medulla
The inner core of the adrenal gland. The adrenal medulla secretes epinephrine and norepinephrine. See Figure 8.1. Compare adrenal cortex. [11]
adrenal steroid hormone
A steroid hormone that is secreted by the adrenal cortex. [11]
adrenaline
See epinephrine. [11]
adrenocorticotropic hormone (ACTH)
A tropic hormone, secreted by the anterior pituitary gland, that controls the production and release of hormones of the adrenal cortex. [ASF 8.3]
adult neurogenesis
The creation of new neurons in the brain of an adult. [1, 13]
afferent
Carrying action potentials toward the brain, or toward one region of interest from another region of interest See Box 2.2. Compare efferent. [2]
affinity
See binding affinity. [4]
afterpotential
The positive or negative change in membrane potential that may follow an action potential. [3]
aggression
Behavior that is intended to cause pain or harm to others. [11]
agnosia
The inability to recognize objects, despite being able to describe them in terms of form and color. Agnosia may occur after localized brain damage. [15]
agonist
A substance that mimics or potentiates the actions of a transmitter or other signaling molecule. Compare antagonist (definition 1). [3, 4]
agraphia
The inability to write. Compare alexia. [15]
AIS
See androgen insensitivity syndrome. [8]
aldosterone
A mineralocorticoid hormone, secreted by the adrenal cortex, that promotes the conservation of sodium by the kidneys. [9]
alexia
The inability to read. See dyslexia. Compare agraphia. [15]
all-or-none property
Referring to the fact that the size (amplitude) of the action potential is independent of the size of the stimulus. See Table 3.2. Compare postsynaptic potential. [3]
allele
Any particular version of a gene.
allomone
A chemical signal that is released outside the body by one species and affects the behavior of other species. See Figure 8.3. Compare pheromone. [8]
allostasis
The combined set of behavioral and physiological adjustments that an individual makes in response to current and predicted behavioral and environmental stressors. [9]
alpha-fetoprotein
A protein found in the plasma of fetuses. In rodents, alpha-fetoprotein binds estrogens and prevents them from entering the brain. [ASF 8.6]
alpha rhythm
A brain potential of 8–12 hertz that occurs during relaxed wakefulness. See Figure 10.9. Compare desynchronized EEG. [10]
alpha-synuclein
A protein that has been implicated in Parkinson’s disease. [ASF 5.5]
ALS
See amyotrophic lateral sclerosis. [ASF 5.5]
Alzheimer’s disease
A form of dementia that may appear in middle age but is more frequent among the aged. [13]
amacrine cell
A specialized retinal cell that contacts both bipolar cells and ganglion cells and is especially significant in inhibitory interactions within the retina. Compare horizontal cell. [7]
amblyopia
Reduced visual acuity that is not caused by optical or retinal impairments. [7, ASF 13.4]
AMH
See anti-müllerian hormone. [8]
amine hormone
Also called monoamine hormone. A hormone composed of a single amino acid that has been modified into a related molecule, such as melatonin or epinephrine. Compare peptide hormone and steroid hormone. [8]
amine neurotransmitter
A neurotransmitter based on modifications of a single amino acid nucleus. Examples include acetylcholine, serotonin, and dopamine. See Table 4.1. Compare amino acid neurotransmitter, gas neurotransmitter, and peptide neurotransmitter. [4]
amino acid neurotransmitter
A neurotransmitter that is itself an amino acid. Examples include GABA, glycine, and glutamate. See Table 4.1. Compare amine neurotransmitter, gas neurotransmitter, and peptide neurotransmitter. [4]
amnesia
Severe impairment of memory. [13]
AMPA receptor
A fast-acting ionotropic glutamate receptor that also binds the glutamate agonist AMPA. Compare NMDA receptor. [ASF 4.2, 13]
amphetamine
A molecule that resembles the structure of the catecholamine transmitters and enhances their activity. [4]
amphetamine psychosis
A delusional and psychotic state, closely resembling acute schizophrenia, that is brought on by repeated use of high doses of amphetamine. [12]
amplitude
Also called intensity. The force that sound exerts per unit area, usually measured as dynes per square centimeter. In practical terms, amplitude corresponds to the volume of a sound. See Box 6.1. [6]
ampulla (pl. ampullae)
An enlarged region of each semicircular canal that contains the receptor cells (hair cells) of the vestibular system. See Figure 6.14. [6]
amusia
A disorder characterized by the inability to discern tunes accurately or to sing. [6]
amygdala
A group of nuclei in the medial anterior part of the temporal lobe. See Figure 2.14. [2, 11]
amyloid plaque
Also called senile plaque. A small area of the brain that has abnormal cellular and chemical patterns. Amyloid plaques correlate with dementia. See Figure 13.34. [13]
amyloid precursor protein (APP)
A protein that, when cleaved by several enzymes, produces beta-amyloid, which can lead to Alzheimer’s disease. [ASF 13.5]
amyotrophic lateral sclerosis (ALS)
Also called Lou Gehrig’s disease. A disease in which motoneurons and their target muscles waste away. [ASF 5.5]
analgesia
Absence of or reduction in pain. [5]
analgesic
Having painkilling properties. [4]
anandamide
An endogenous substance that binds the cannabinoid receptor molecule. [4]
androgen
Any of a class of hormones that includes testosterone and other male hormones. See Figure 8.13. [8]
androgen insensitivity syndrome (AIS)
A syndrome caused by a mutation of the androgen receptor gene that renders tissues insensitive to androgenic hormones like testosterone. Affected XY individuals are phenotypic females, but they have internal testes and regressed internal genital structures. See Figure 8.27. [8]
angel dust
See phencyclidine. [12]
angiotensin II
A hormone that is produced in the blood by the action of renin and that may play a role in the control of thirst. [9]
angular gyrus
A brain region in which strokes can lead to word blindness.
anion
A negatively charged ion, such as a protein or a chloride ion. Compare cation. [3]
anomia
The inability to name persons or objects readily. [15]
anorexia nervosa
A syndrome in which individuals severely deprive themselves of food. [9]
anosmia
The inability to detect odors. [6]
ANP
See atrial natriuretic peptide. [9]
antagonist
1. A substance that blocks or attenuates the actions of a transmitter or other signaling molecule. Compare agonist. [3, 4] 2. A muscle that counteracts the effect of another muscle. Compare synergist. [5]
anterior
Also called rostral. In anatomy, toward the head end of an organism. See Box 2.2. Compare posterior. [2]
anterior cerebral artery
Either of two large arteries, arising from the carotid arteries, that provide blood to the anterior poles and medial surfaces of the cerebral hemispheres. Compare middle cerebral artery and posterior cerebral artery. [ASF 2.1]
anterior pituitary
The front division of the pituitary gland. It secretes tropic hormones. See Figures 8.1, 8.12. Compare posterior pituitary. [8]
anterograde amnesia
Difficulty in forming new memories beginning with the onset of a disorder. Compare retrograde amnesia. [13]
anterolateral system
Also called spinothalamic system. A somatosensory system that carries most of the pain information from the body to the brain. See Figure 5.12. Compare dorsal column system. [5]
antibody
Also called immunoglobulin. A large protein that recognizes and permanently binds to particular shapes, normally as part of the immune system attack on foreign particles. [ASF 11.4, App]
antidepressant
A drug that relieves the symptoms of depression. Major categories include monoamine oxidase inhibitors, tricyclics, and selective serotonin reuptake inhibitors. [4]
antidiuretic hormone (ADH)
See vasopressin.
anti-müllerian hormone (AMH)
Also called müllerian regression hormone. A protein hormone secreted by the fetal testes that inhibits müllerian duct development. [8]
antipsychotic
Also called neuroleptic. Any of a class of antipsychotic drugs that alleviate symptoms of schizophrenia, typically by blocking dopamine receptors. [4, 12]
anxiety disorder
Any of a class of psychological disorders that includes recurrent panic states, generalized persistent anxiety disorders, and posttraumatic stress disorder. [12]
anxiolytic
A substance that is used to combat anxiety. Examples include alcohol, opiates, barbiturates, and the benzodiazepines. [4, 12]
aphasia
An impairment in language understanding and/or production that is caused by brain injury. [15]
ApoE
See apolipoprotein E. [ASF 13.5]
apolipoprotein E (ApoE)
A protein that may help break down beta-amyloid. Individuals carrying the ApoE4 allele are more likely to develop Alzheimer’s disease. [ASF 13.5]
apoptosis
See cell death. [13]
APP
See amyloid precursor protein. [ASF 13.5]
appetitive behavior
The second stage of mating behavior. It helps establish or maintain sexual interaction. See Figure 8.16. [8]
apraxia
An impairment in the ability to carry out complex sequential movements, even though there is no muscle paralysis. [5, 15]
arachnoid
The thin covering (one of the three meninges) of the brain that lies between the dura mater and the pia mater. See Figure 2.8. [2]
arcuate fasciculus
A fiber tract classically viewed as a connection between Wernicke’s speech area and Broca’s speech area. See Figure 15.9. [15]
arcuate nucleus
An arc-shaped hypothalamic nucleus implicated in appetite control. See Figure 9.15 . [9]
area 17
See primary visual cortex.
arginine vasopressin (AVP)
See vasopressin.
aromatase
An enzyme that converts many androgens into estrogens. [ASF 8.6]
aromatization
The chemical reaction that converts testosterone to estradiol, and other androgens to other estrogens. [ASF 8.6]
aromatization hypothesis
The hypothesis that testicular androgens enter the brain and are converted there into estrogens to masculinize the developing nervous system of some rodents. [ASF 8.6]
arousal
The global, nonselective level of alertness of an individual.
Asperger’s syndrome
Also called high-functioning autism. A syndrome characterized by difficulties in social cognitive processing. It is usually accompanied by strong language skills. Compare autism. [ASF 13.4]
associative learning
A type of learning in which an association is formed between two stimuli or between a stimulus and a response. It includes both classical and instrumental conditioning. Compare nonassociative learning. [13]
astereognosis
The inability to recognize objects by touching and feeling them. [15]
astrocyte
A star-shaped glial cell with numerous processes (extensions) that run in all directions. See Figure 2.5. [2]
ataxia
A loss of movement coordination, often caused by disease of the cerebellum. [5]
atrial natriuretic peptide (ANP)
A hormone, secreted by the heart, that normally reduces blood pressure, inhibits drinking, and promotes the excretion of water and salt at the kidneys. [9]
attention
Also called selective attention. A state or condition of selective awareness or perceptual receptivity, by which specific stimuli are selected for enhanced processing. [14]
attention deficit hyperactivity disorder (ADHD)
A syndrome characterized by distractibility, impulsiveness, and hyperactivity that, in children, interferes with school performance. [14, ASF 13.4]
attentional blink
The reduced ability of subjects to detect a target stimulus if it follows another target stimulus by about 200–450 milliseconds.
attentional bottleneck
A filter created by the limits intrinsic to our attentional processes, whose effect is that only the most important stimuli are selected for special processing. [14]
attentional spotlight
The shifting of our limited selective attention around the environment to highlight stimuli for enhanced processing. [14]
atypical antipsychotic
Also called atypical neuroleptic. An antipsychotic drug that has actions other than or in addition to the dopamine D2 receptor antagonism that characterizes the typical antipsychotics. [4, 12]
auditory canal
See ear canal. [6]
auditory N1 effect
A negative deflection of the event-related potential, occurring about 100 milliseconds after stimulus presentation, that is enhanced for selectively attended auditory input compared with ignored input. Compare visual P1 effect. [14]
auditory P300
See P3 effect. [14]
aura
In epilepsy, the unusual sensations or premonition that may precede the beginning of a seizure. [3]
autism spectrum disorder (ASD)
A disorder, arising during childhood, that is characterized by social withdrawal and perseverative behavior. Compare Asperger’s syndrome. [ASF 13.4]
autobiographical memory
See episodic memory. [13]
autocrine
Referring to a signal that is secreted by a cell into its environment and that feeds back to the same cell.
autoimmune disorder
A disorder caused when the immune system mistakenly attacks a person’s own body, thereby interfering with normal functioning. [ASF 5.5]
autonomic ganglion
A collection of nerve cell bodies, belonging to the autonomic division of the peripheral nervous system, that is found in any of various locations and contributes to the innervation of major organs.
autonomic nervous system
A part of the peripheral nervous system that provides the main neural connections to glands and to smooth muscles of internal organs. Its two divisions (sympathetic and parasympathetic) act in opposite fashion. See Figure 2.9. [2]
autoradiography
A staining technique that shows the distribution of radioactive chemicals in tissues. See Boxes 2.1, 8.1. [2, 8]
autoreceptor
A receptor for a synaptic transmitter that is located in the presynaptic membrane and tells the axon terminal how much transmitter has been released. [4]
AVP
See arginine vasopressin. [8]
axo-axonic synapse
A synapse at which a presynaptic axon terminal synapses onto the axon terminal of another neuron. Compare axo-dendritic synapse, axo-somatic synapse, and dendro-dendritic synapse. [3]
axo-dendritic synapse
A synapse at which a presynaptic axon terminal synapses onto a dendrite of the postsynaptic neuron, either via a dendritic spine or directly onto the dendrite itself. Compare axo-axonic synapse, axo-somatic synapse, and dendro-dendritic synapse. [3]
axo-somatic synapse
A synapse at which a presynaptic axon terminal synapses onto the cell body (soma) of the postsynaptic neuron. Compare axo-axonic synapse, axo-dendritic synapse, and dendro-dendritic synapse. [3]
axon
Also called nerve fiber. A single extension from the nerve cell that carries action potentials from the cell body toward the axon terminals. Functionally, the axon is the conduction zone of the neuron. See Figures 2.1, 2.3. [2]
axon collateral
A branch of an axon. [2]
axon hillock
The cone-shaped area on the cell body from which the axon originates. See Figure 2.4. [2, 3]
axon terminal
Also called synaptic bouton. The end of an axon or axon collateral, which forms a synapse on a neuron or other target cell. Functionally, the axon terminals are the output zone of the neuron. See Figures 2.1, 2.3 [2]
axonal transport
The transportation of materials from the neuronal cell body toward the axon terminals, and from the axon terminals back toward the cell body. [2]

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B

B cell
See B lymphocyte. [ASF 11.4]
B lymphocyte
Also called B cell. An immune system cell, formed in the bone marrow (hence the B), that mediates humoral immunity. Compare T lymphocyte. [ASF 11.4]
Balint’s syndrome
A disorder, caused by damage to both parietal lobes, that is characterized by difficulty in steering visual gaze (oculomotor ataxia), in accurately reaching for objects using visual guidance (optic ataxia), and in directing attention to more than one object or feature at a time (simultagnosia). [14]
bar detector
See simple cortical cell. [7]
barbiturate
An early anxiolytic drug and sleep aid that has depressant activity in the nervous system. [4]
bariatrics
The branch of medicine that deals with the causes, prevention, and treatment of obesity. [9]
baroreceptor
A pressure receptor in the heart or a major artery that detects a change in blood pressure. [9]
basal
“Toward the base” or “toward the bottom” of a structure. See Box 2.2. [2]
basal forebrain
A region, ventral to the basal ganglia, that is the major source of acetylcholine in the brain and has been implicated in sleep. [4, 10]
basal ganglia
A group of forebrain nuclei, including the caudate nucleus, globus pallidus, and putamen, found deep within the cerebral hemispheres. See Figures 2.14, 2.15, 5.27. [2, 5, 13]
basal metabolism
The consumption of energy to fuel processes such as heat production, maintenance of membrane potentials, and all the other basic life-sustaining functions of the body. [9]
basilar artery
An artery, formed by the fusion of the vertebral arteries, that supplies blood to the brainstem and to the posterior cerebral arteries. [ASF 2.1]
basilar membrane
A membrane in the cochlea that contains the principal structures involved in auditory transduction. See Figures 6.1, 6.2. [6]
behavioral intervention
An approach to finding relations between body variables and behavioral variables that involves intervening in the behavior of an organism and looking for resultant changes in body structure or function. See Figure 1.9. Compare somatic intervention. [1]
behavioral medicine
See health psychology. [11]
behavioral neuroscience
See biological psychology. [1]
benzodiazepine
Any of a class of antianxiety drugs that are agonists of GABAA receptors in the central nervous system. One example is diazepam (Valium). [4, 12]
beta activity
See desynchronized EEG. [10]
beta-amyloid
A protein that accumulates in amyloid plaques in Alzheimer’s disease. [13]
beta-secretase
An enzyme that cleaves amyloid precursor protein, forming beta-amyloid, which can lead to Alzheimer’s disease. See also presenilin. [ASF 13.5]
between-participants experiment
An experiment in which an experimental group of individuals is compared with a control group of individuals that have been treated identically in every way except that they haven’t received the experimental manipulation. Compare within-participants experiment. [1]
binaural
Pertaining to two ears. Compare monaural.
binding affinity
Also called simply affinity. The propensity of molecules of a drug (or other ligand) to bind to receptors. Drugs with high affinity for their receptors are effective even at low doses. [4]
binding problem
The question of how the brain understands which individual attributes blend together into a single object, when these different features are processed by different regions in the brain. [14]
binge eating
The rapid intake of large quantities of food, often poor in nutritional value and high in calories. [9]
binocular
Referring to two-eyed processes. [7]
binocular deprivation
Depriving both eyes of form vision, as by sealing the eyelids. Compare monocular deprivation. [ASF 13.4]
bioavailable
Referring to a substance, usually a drug, that is present in the body in a form that is able to interact with physiological mechanisms. [4]
biological psychology
Also called behavioral neuroscience, brain and behavior, and physiological psychology. The study of the biological bases of psychological processes and behavior. [1]
biological rhythm
A regular periodic fluctuation in any living process. [10]
biotransformation
The process in which enzymes convert a drug into a metabolite that is itself active, possibly in ways that are substantially different from the actions of the original substance. [4]
bipolar cell
An interneuron in the retina that receives information from rods and cones and passes the information to retinal ganglion cells. See Figure 7.3. Compare amacrine cell and horizontal cell. [7]
bipolar disorder
A psychiatric disorder characterized by periods of depression that alternate with excessive, expansive moods. [12]
bipolar neuron
A nerve cell that has a single dendrite at one end and a single axon at the other end. See Figure 2.3. Compare unipolar neuron and multipolar neuron. [2]
blind spot
The portion of the visual field from which light falls on the optic disc. [7]
blindsight
The paradoxical phenomenon whereby, within a scotoma, a person cannot consciously perceive visual cues but may still be able to make some visual discrimination. [7]
blood-brain barrier
The protective property of cerebral blood vessels that impedes the movement of some harmful substances from the blood stream into the brain. [2, 4]
blotting
Transferring DNA, RNA, or protein fragments to nitrocellulose following separation via gel electrophoresis. The blotted substance can then be labeled. See Appendix Figure A.3. [App]
brain and behavior
See biological psychology. [1]
brain self-stimulation
The process in which animals will work to provide electrical stimulation to particular brain sites, presumably because the experience is very rewarding. [11]
brainstem
The region of the brain that consists of the midbrain, the pons, and the medulla. [2]
brightness
One of three basic dimensions of light perception, varying from dark to light. Compare hue and saturation. [7]
Broca’s aphasia
See nonfluent aphasia. [15]
Broca’s area
A region of the frontal lobe of the brain that is involved in the production of speech. See Figures 15.6, 15.8, 15.9. Compare Wernicke’s area. [15]
brown fat
Also called brown adipose tissue. A specialized type of fat tissue that generates heat through intense metabolism. [ASF 9.1]
bulimia
Also called bulimia nervosa. A syndrome in which individuals periodically gorge themselves, usually with “junk food,” and then either vomit or take laxatives to avoid weight gain. [9]
bungarotoxin
A neurotoxin, isolated from the venom of the many-banded krait, that selectively blocks acetylcholine receptors. [3]

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C

C fiber
A small, unmyelinated axon that conducts pain information slowly and adapts slowly. [5]
c-fos">c-fos
An immediate early gene commonly used to identify activated neurons. See Box 2.1.
CAH
See congenital adrenal hyperplasia. [8]
calcium ion (Ca2+)
A calcium atom that carries a double positive charge. [3]
carotid artery
Either of the two major arteries that ascend the left and right sides of the neck to the brain, supplying blood to the anterior and middle cerebral arteries. The branch that enters the brain is called the internal carotid artery. [ASF 2.1]
castration
Removal of the gonads, usually the testes. [8]
CAT
See computerized axial tomography. [2]
cataplexy
Sudden loss of muscle tone, leading to collapse of the body without loss of consciousness. Cataplexy is sometimes a component of narcoleptic attacks. [10]
cation
A positively charged ion, such as a potassium or sodium ion. Compare anion. [3]
cauda equina
Literally, “horse’s tail” (in Latin). The caudalmost spinal nerves, which extend beyond the spinal cord proper to exit the spinal column.
caudal
See posterior. See Box 2.2. [2]
caudate nucleus
One of the basal ganglia. It has a long extension or tail. See Figure 2.14. [2]
causality
The relation of cause and effect, such that we can conclude that an experimental manipulation has specifically caused an observed result. [1]
CBT
See cognitive behavioral therapy. [12]
CCK
See cholecystokinin. [9]
cell body
Also called soma. The region of a neuron that is defined by the presence of the cell nucleus. Functionally, the cell body is the integration zone of the neuron. See Figures 2.1, 2.3. [2]
cell-cell interaction
The general process during development in which one cell affects the differentiation of other, usually neighboring, cells. [13]
cell death
Also called apoptosis. The developmental process during which “surplus” cells die. See Figure 13.25. [13]
cell differentiation
The developmental stage in which cells acquire distinctive characteristics, such as those of neurons, as a result of expressing particular genes. See Figure 13.25. [13, App]
cell membrane
The lipid bilayer that ensheathes a cell. [3]
cell migration
The movement of cells from site of origin to final location. See Figure 13.25. [13]
cell nucleus
The spherical central structure of a cell that contains the chromosomes. [App]
central deafness
A hearing impairment in which the auditory areas of the brain fail to process and interpret action potentials from sound stimuli in meaningful ways, usually as a consequence of  damage in auditory brain areas. See Figure 6.11. Compare conduction deafness and sensorineural deafness. [6]
central modulation of sensory information
The process in which higher brain centers, such as the cortex and thalamus, suppress some sources of sensory information and amplify others. [5]
central nervous system (CNS)
The portion of the nervous system that includes the brain and the spinal cord. See Figures 2.6, 2.12. Compare peripheral nervous system. [2]
central sulcus
A fissure that divides the frontal lobe from the parietal lobe. See Figure 2.10. [2]
cerebellum
A structure located at the back of the brain, dorsal to the pons, that is involved in the central regulation of movement and in some forms of learning. See Figures 2.10, 2.12, 2.16, 5.27. [2, 5, 13]
cerebral arteries
The three pairs of large arteries within the skull that supply blood to the cerebral cortex. [2]
cerebral cortex
Also called simply cortex. The thick and convoluted outermost rind of the cerebral hemispheres, consisting largely of nerve cell bodies and their branches. See Figure 2.13. [2]
cerebral hemisphere
One of the two halves—right or left—of the forebrain. See Figure 2.12. [2]
cerebrocerebellum
The lowermost part of the cerebellum, consisting especially of the lateral parts of each cerebellar hemisphere. It is implicated in planning complex movements. Compare spinocerebellum and vestibulocerebellum. [ASF 5.4]
cerebrospinal fluid (CSF)
The fluid that fills the cerebral ventricles. See Figure 2.17. [2]
cerveau isolé
See isolated forebrain. [10]
cervical
Referring to the topmost eight segments of the spinal cord, in the neck region. See Figures 2.8, 2.9. Compare thoracic, lumbar, sacral, and coccygeal. [2]
change blindness
A failure to notice changes in comparisons of two alternating static visual scenes.
ChAT
See choline acetyltransferase. [ASF 4.1]
chemical transmitter
See neurotransmitter. [2, 3]
chloride ion (Cl–)
A chlorine atom that carries a negative charge. [3]
chlorpromazine
An early antipsychotic drug that revolutionized the treatment of schizophrenia. [12]
cholecystokinin (CCK)
A peptide hormone that is released by the gut after ingestion of food that is high in protein and/or fat. [9]
choline acetyltransferase (ChAT)
An important enzyme involved in the synthesis of the neurotransmitter acetylcholine. [ASF 4.1]
cholinergic
Referring to cells that use acetylcholine as their synaptic transmitter. [3, 4]
choroid plexus
A specialized membrane lining the ventricles that produces cerebrospinal fluid by filtering blood. [2]
chromosome
A complex of condensed strands of DNA and associated protein molecules. Chromosomes are found in the nucleus of cells. [App]
chronic traumatic encephalopathy (CTE)
Also called dementia pugilistica or punch-drunk syndrome. A form of dementia that may develop following multiple concussions, such as in athletes engaged in contact sports. See Box 15.3. [15]
ciliary muscle
One of the muscles that control the shape of the lens inside the eye, focusing an image on the retina. See Figure 7.1. [7]
CIMT
See constraint-induced movement therapy. [15]
cingulate cortex
Also called cingulum. A region of medial cerebral cortex that lies dorsal to the corpus callosum. [5]
cingulate gyrus
Also called cingulate cortex or cingulum. A strip of cortex, found in the frontal and parietal midline, that is part of the limbic system and is implicated in many cognitive functions. See Figures 2.14, 2.16. [2]
circadian rhythm
A pattern of behavioral, biochemical, or physiological fluctuation that has a 24-hour period. [10]
circle of Willis
A structure at the base of the brain that is formed by the joining of the carotid and basilar arteries. [ASF 2.1]
circumventricular organ
Any of multiple distinct sites that lie in the wall of a cerebral ventricle and monitor the composition of the cerebrospinal fluid. See Figure 9.8. [9]
classical conditioning
Also called Pavlovian conditioning. A type of associative learning in which an originally neutral stimulus (the conditioned stimulus, or CS)—through pairing with another stimulus (the unconditioned stimulus, or US) that elicits a particular response—acquires the power to elicit that response when presented alone. A response elicited by the US is called an unconditioned response (UR); a response elicited by the CS alone is called a conditioned response (CR). See Figure 13.9. Compare instrumental conditioning. [13]
clitoris
The female phallus. Compare penis. [8]
cloacal exstrophy
A rare medical condition in which XY individuals are born completely lacking a penis. [8]
clones
Asexually produced organisms that are genetically identical. [13, App]
clozapine
An atypical antipsychotic. [12]
CNS
See central nervous system. [2]
cocaine
A drug of abuse, derived from the coca plant, that acts by enhancing catecholamine neurotransmission. [4]
coccygeal
Referring to the lowest spinal vertebra (the coccyx, also known as the “tailbone”). See Figure 2.9. Compare cervical, thoracic, lumbar, and sacral. [2]
cochlea
A snail-shaped structure in the inner ear that contains the primary receptor cells for hearing. See Figure 6.1. [6]
cochlear implant
An electromechanical device that detects sounds and selectively stimulates nerves in different regions of the cochlea via surgically implanted electrodes. [6]
cochlear nucleus
Either of two brainstem nuclei—left and right—that receive input from auditory hair cells and send output to the superior olivary nuclei. See Figure 6.6. [6]
cocktail party effect
The selective enhancement of attention in order to filter out distracters, as you might do while listening to one person talking in the midst of a noisy party. [14]
codon
A set of three nucleotides that encodes one particular amino acid. A series of codons determines the structure of a peptide or protein. [App]
cognitive behavioral therapy (CBT)
Psychotherapy aimed at correcting negative thinking and consciously changing behaviors as a way of changing feelings. [12]
cognitive map
A mental representation of the relative spatial organization of objects and information. [13]
cognitively impenetrable
Referring to basic neural processing operations that cannot be experienced through introspection—in other words, that are unconscious. [14]
coitus
See copulation. [8]
collateral sprouting
The formation of a new branch on an axon, usually in response to the uncovering of unoccupied postsynaptic sites. [ASF 15.4]
communication
Information transfer between two individuals. [15]
complex cortical cell
A cell in the visual cortex that responds best to a bar of a particular size and orientation anywhere within a particular area of the visual field and that needs movement to make it respond actively. Compare simple cortical cell. [7]
complex environment
See enriched condition. [13]
complex partial seizure
In epilepsy, a type of seizure that doesn’t involve the entire brain and therefore can cause a wide variety of symptoms. [3]
computerized axial tomography (CAT or CT)
A noninvasive technique for examining brain structure through computer analysis of X-ray absorption at several positions around the head. See Figure 2.19. Compare magnetic resonance imaging. [2]
concordance
Sharing of a characteristic by both individuals of a pair of twins. [12]
concussion
A form of closed head injury caused by a jarring blow to the head, resulting in damage to the tissue of the brain with short- or long-term consequences for cognitive function. [15]
conduction aphasia
An impairment in the ability to repeat words and sentences. [15]
conduction deafness
A hearing impairment in which the ears fail to convert sound vibrations in air into waves of fluid in the cochlea. It is associated with defects of the external ear or middle ear. See Figure 6.11. Compare central deafness and sensorineural deafness. [6]
conduction velocity
The speed at which an action potential is propagated along the length of an axon. [3]
conduction zone
The part of a neuron—typically the axon—over which the action potential is actively propagated. See Figures 2.1, 2.3. Compare input zone, integration zone, and output zone. [2]
cone
Any of several classes of photoreceptor cells in the retina that are responsible for color vision. See Figure 7.3. Compare rod. [7]
confabulate
To fill in a gap in memory with a falsification. Confabulation is often seen in Korsakoff’s syndrome. [13]
congenital adrenal hyperplasia (CAH)
Any of several genetic mutations that can cause a female fetus to be exposed to adrenal androgens, resulting in partial masculinization at birth. [8]
conjunction search
A search for an item that is based on two or more features (e.g., size and color) that together distinguish the target from distracters that may share some of the same attributes. Compare feature search. [14]
connectionist model of aphasia
Also called Wernicke-Geschwind model. A theory proposing that left-hemisphere language deficits result from disconnection between the brain regions in a language network, each of which serves a particular linguistic function. Compare motor theory of language. [15]
consciousness
The state of awareness of one’s own existence, thoughts, emotions, and experiences. [1, 14]
conserved
In the context of evolution, referring to a trait that is passed on from a common ancestor to two or more descendant species. [1]
consolidation
The second process in the memory system, in which information in short-term memory is transferred to long-term memory. See Figure 13.13. Compare encoding and retrieval. [13]
constraint-induced movement therapy (CIMT)
A therapy for recovery of movement after stroke or injury in which the person’s unaffected limb is constrained while he is required to perform tasks with the affected limb. [15]
contralateral
In anatomy, pertaining to a location on the opposite side of the body. See Box 2.2. Compare ipsilateral. [2, 15]
control group
In research, a group of individuals that are identical to those in an experimental (or test) group in every way except that they do not receive the experimental treatment or manipulation. The experimental group is then compared with the control group to assess the effect of the treatment. [1]
convergence
The phenomenon of neural connections in which many cells send signals to a single cell. Compare divergence. [ASF 3.2, 7]
Coolidge effect
The propensity of an animal that appears sexually satiated with a current partner to resume sexual activity when provided with a new partner. [8]
copulation
Also called coitus. The sexual act. [8]
cornea
The transparent outer layer of the eye, whose curvature is fixed. The cornea bends light rays and is primarily responsible for forming the image on the retina. See Figure 7.1. [7]
coronal plane
Also called frontal plane or transverse plane. The plane that divides the body or brain into front and back parts. See Box 2.2. Compare horizontal plane and sagittal plane. [2]
corpus callosum
The main band of axons that connects the two cerebral hemispheres. See Figures 2.11, 2.16. [2, 15]
corpus luteum (pl. corpora lutea)
The structure that forms from the collapsed ovarian follicle after ovulation. The corpora lutea are a major source of progesterone. [8, ASF 8.3]
correlation
The tendency of two measures to vary in concert, such that a change in one measure is matched by a change in the other. [1]
cortex (pl. cortices)
The outer layer of a structure. See also cerebral cortex and neocortex. [2]
cortical column
One of the vertical columns that constitute the basic organization of the cerebral cortex. [2]
cortical deafness
A form of central deafness, caused by damage to both sides of the auditory cortex, that is characterized by difficulty in recognizing all complex sounds, whether verbal or nonverbal. [6]
corticospinal system
See pyramidal system. [5]
cortisol
A glucocorticoid stress hormone of the adrenal cortex. [11]
covert attention
Attention in which the focus can be directed independently of sensory orientation (e.g., you’re attending to one sensory stimulus while looking at another). Compare overt attention. [14]
cranial nerve
One of the 12 pairs of nerves that arise directly from the brain rather than the spinal cord, supplying senory and motor connections to the head and neck. See Figure 2.7. Compare spinal nerve. [2]
crib death
See sudden infant death syndrome. [10]
critical period
See sensitive period. [15]
cross-tolerance
A condition in which the development of tolerance for one drug causes an individual to develop tolerance for another drug. [4]
crystallization
The final stage of birdsong formation, in which fully formed adult song is achieved. [ASF 15.3]
CSF
See cerebrospinal fluid. [2]
CT
See computerized axial tomography. [2]
CTE
See chronic traumatic encephalopathy. [15]
curare
A neurotoxin that causes paralysis by blocking acetylcholine receptors in muscle. [3]
Cushing’s syndrome
A condition in which levels of adrenal glucocorticoids are abnormally high. [ASF 12.2]
cytokine
A protein that induces the proliferation of other cells, as in the immune system. Examples include interleukins and interferons. [ASF 11.4]
cytoplasm
See intracellular fluid. [3]

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D

DA
See dopamine. [4]
dB
See decibel. [6]
DBS
See deep brain stimulation. [12]
death gene
A gene that is expressed only when a cell becomes committed to natural cell death (apoptosis). [13]
decibel (dB)
A measure of sound intensity, perceived as loudness. See Box 6.1. [6]
declarative memory
A memory that can be stated or described. See Figures 13.4, 13.12. Compare nondeclarative memory. [13]
decomposition of movement
Difficulty of movement in which gestures are broken up into individual segments instead of being executed smoothly; it is a symptom of cerebellar lesions. [5]
decorticate rage
Also called sham rage. Sudden intense rage characterized by actions (such as snarling and biting in dogs) that lack clear direction. [11]
deep brain stimulation (DBS)
Mild electrical stimulation through an electrode that is surgically implanted deep in the brain. [12]
deep dyslexia
Acquired dyslexia in which the patient reads a word as another word that is semantically related. Compare surface dyslexia. [15]
default mode network
A circuit of brain regions that is active during quiet introspective thought. [14]
degradation
The chemical breakdown of a neurotransmitter into inactive metabolites. [3]
dehydration
Excessive loss of water.
delayed non-matching-to-sample task
A test in which the subject must respond to the unfamiliar stimulus in a pair of stimuli. See Figure 13.5. [13]
delta-9-tetrahydrocannabinol (THC)
The major active ingredient in marijuana. [4]
delta wave
The slowest type of EEG wave, characteristic of stage 3 sleep. See Figure 10.10. [10]
delusion
A false belief strongly held in spite of contrary evidence. [12]
dementia
Drastic failure of cognitive ability, including memory failure and loss of orientation. [13]
dementia pugilistica
See chronic traumatic encephalopathy. [15]
dendrite
An extension of the cell body that receives information from other neurons. Functionally, the dendrites are the input zone of the neuron. See Figures 2.1, 2.3. [2]
dendritic spine
An outgrowth along the dendrite of a neuron. See Figure 2.4. [2]
dendro-dendritic synapse
A synapse at which a synaptic connection forms between the dendrites of two neurons. Compare axo-axonic synapse, axo-dendritic synapse, and axo-somatic synapse. [3]
dentate gyrus
A strip of gray matter in the hippocampal formation. [13]
deoxyribonucleic acid (DNA)
A nucleic acid that is present in the chromosomes of cells and codes hereditary information. Compare ribonucleic acid. [App]
dependent variable
The factor that an experimenter measures to monitor a change in response to changes in an independent variable. [1]
depolarization
A decrease in membrane potential (the interior of the neuron becomes less negative). See Figure 3.5. Compare hyperpolarization. [3]
depressant
A drug that reduces the excitability of neurons. Compare stimulant. [4]
depression
A psychiatric condition characterized by such symptoms as an unhappy mood; loss of interests, energy, and appetite; and difficulty concentrating. See also bipolar disorder. [12]
dermatome
A strip of skin innervated by a particular spinal nerve. [5]
desynchronized EEG
Also called beta activity. A pattern of EEG activity comprising a mix of many different high frequencies with low amplitude. Compare alpha rhythm. [10]
dexamethasone suppression test
A test of pituitary-adrenal function in which the subject is given dexamethasone, a synthetic glucocorticoid hormone, which should cause a decline in the production of adrenal corticosteroids. [ASF 12.2]
DHT
See dihydrotestosterone. [8]
diabetes mellitus
A condition, characterized by excessive glucose in the blood and urine and by reduced glucose utilization by body cells, that is caused by the failure of insulin to induce glucose absorption. [9]
dichotic presentation
The simultaneous delivery of different stimuli to both the right and the left ears at the same time. See Figure 15.2. [15]
diencephalon
The posterior part of the fetal forebrain, which will become the thalamus and hypothalamus in the adult brain. See Figures 2.12, 13.24. Compare telencephalon. [2]
differentiation
See cell differentiation. [13, App]
diffusion
The spontaneous spread of molecules from an area of high concentration to an area of low concentration until a uniform concentration is achieved. See Figure 3.3. Compare osmosis. [3, 9]
diffusion tensor imaging (DTI)
A modified form of MRI imaging in which the diffusion of water in a confined space is exploited to produce images of axonal fiber tracts. [15]
digestion
The process by which food is broken down to provide energy and nutrients. [ASF 9.3]
dihydrotestosterone (DHT)
The 5-alpha-reduced metabolite of testosterone. DHT is a potent androgen that is principally responsible for the masculinization of the external genitalia in mammals. [8]
distal
In anatomy, toward the periphery of an organism or toward the end of a limb. See Box 2.2. Compare proximal. [2]
diurnal
Active during the light periods of the daily cycle. Compare nocturnal. [10]
divergence
The phenomenon of neural connections in which one cell sends signals to many other cells. Compare convergence. [ASF 3.2]
divided-attention task
A task in which the subject is asked to focus attention on two or more stimuli simultaneously. Compare sustained-attention task. [14]
dizygotic
Referring to twins derived from separate eggs (fraternal twins). Compare monozygotic. [12]
DNA
See deoxyribonucleic acid. [App]
DNA sequencing
The process by which the order of nucleotides in a gene is identified. [App]
dopamine (DA)
A monoamine transmitter found in the midbrain—especially the substantia nigra—and in the basal forebrain. See Figure 4.4; Table 4.1. [4]
dopamine hypothesis
The idea that schizophrenia results from either excessive levels of synaptic dopamine or excessive postsynaptic sensitivity to dopamine. [12]
dopaminergic
Referring to cells that use dopamine as their synaptic transmitter. [4]
dorsal
In anatomy, toward the back of the body or the top of the brain. See Box 2.2. Compare ventral. [2]
dorsal column system
A somatosensory system that delivers most touch stimuli via the dorsal columns of spinal white matter to the brain. See Figure 5.7. Compare anterolateral system. [5]
dorsomedial thalamus
A limbic system structure that is connected to the hippocampus. [13]
dose-response curve (DRC)
A formal graph of a drug’s effects (on the y-axis) versus the dose given (on the x-axis). See Figure 4.6. [4]
down-regulation
A compensatory decrease in receptor availability at the synapses of a neuron. Compare up-regulation. [4]
DRC
See dose-response curve. [4]
drug tolerance
Also called simply tolerance. A condition in which, with repeated exposure to a drug, an individual becomes less responsive to a constant dose. [4]
DTI
See diffusion tensor imaging. [15]
DTI tractography
Also called fiber tracking. Visualization of the orientation and terminations of white matter tracts in the living brain via diffusion tensor imaging. [15]
dualism
The notion, promoted by René Descartes, that the mind has an immaterial aspect that is distinct from the material body and brain. [1]
duplex theory
A theory that we localize sound by combining information about intensity differences and latency differences between the two ears.
dura mater
The outermost of the three meninges that surround the brain and spinal cord. See also pia mater and arachnoid. See Figure 2.8. [2]
dynorphin
One of the three kinds of endogenous opioids. Compare endorphin and enkephalin. See Table 4.1. [4]
dyskinesia
Difficulty or distortion in voluntary movement. See Box 12.1.[12]
dyslexia
Also called alexia. A reading disorder attributed to brain impairment. [15]
dysphoria
Unpleasant feelings; the opposite of euphoria. [4]
dystrophin
A protein that is needed for normal muscle function. Dystrophin is defective in some forms of muscular dystrophy. [ASF 5.5]

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E

ear canal
Also called auditory canal. The tube leading from the pinna to the tympanic membrane. [6]
eardrum
See tympanic membrane. [6]
easy problem of consciousness
Understanding how particular patterns of neural activity create specific conscious experiences by reading brain activity directly from people’s brains as they’re having particular experiences. Compare hard problem of consciousness. [14]
EC
See enriched condition. [13]
ecological niche
The unique assortment of environmental opportunities and challenges to which each organism is adapted. [10]
Ecstasy
See MDMA. [4]
ECT
See electroconvulsive shock therapy. [12]
ectoderm
The outer cellular layer of the developing embryo, giving rise to the skin and the nervous system. [13]
ectotherm
An animal whose body temperature is regulated by, and whose heat comes mainly from, the environment. Examples include snakes and bees. Compare endotherm. [9]
ED50
Effective dose 50%; the dose of a drug that is required to produce half of its maximal effect. See Figure 4.6. Compare LD50.
edema
The swelling of tissue in response to injury. [2]
edge detector
See simple cortical cell. [7]
EEG
See electroencephalography. [3, 10]
efferent
Carrying action potentials away from the brain, or away from one region of interest toward another region of interest. See Box 2.2. Compare afferent. [2]
efficacy
Also called intrinsic activity. The extent to which a drug activates a response when it binds to a receptor. Receptor antagonist drugs have low efficacy; receptor agonists have high efficacy. See Figure 4.6. [4]
egg
See ovum. [8]
ejaculation
The forceful expulsion of semen from the penis. [8]
electrical synapse
Also called gap junction. The region between neurons where the presynaptic and postsynaptic membranes are so close that the action potential can jump to the postsynaptic membrane without first being translated into a chemical message. [ASF 3.1]
electroconvulsive shock therapy (ECT)
A last-resort treatment for unmanageable depression, in which a strong electrical current is passed through the brain, causing a seizure. [12]
electroencephalography (EEG)
The recording of gross electrical activity of the brain via large electrodes placed on the scalp. The abbreviation EEG may refer either to the process of encephalography or to its product, the encephalogram. See Figures 3.15, 10.9. [3, 10]
electromyography (EMG)
The electrical recording of muscle activity. See Figure 5.15. [5]
electrostatic pressure
The propensity of charged molecules or ions to move toward areas with the opposite charge. [3]
embryo
The earliest stage in a developing animal. Humans are considered to be embryos until 8–10 weeks after conception. Compare fetus. [13]
embryonic stem cell
A cell, derived from an embryo, that has the capacity to form any type of tissue. [15]
EMG
See electromyography. [5]
emotion
A subjective mental state that is usually accompanied by distinctive behaviors as well as involuntary physiological changes. [11]
encéphale isolé
See isolated brain. [10]
encoding
The first process in the memory system, in which the information entering sensory channels is passed into short-term memory. See Figure 13.13. Compare consolidation and retrieval. [13]
endocannabinoid
An endogenous ligand of cannabinoid receptors, thus a marijuana analog that is produced by the brain.[4, 9]
endocrine
Referring to glands that release chemicals to the interior of the body. These glands secrete the principal hormones used by the body. See Figure 8.3. [8]
endocrine gland
A gland that secretes hormones into the bloodstream to act on distant targets. See Figure 8.1. [8]
endogenous
Produced inside the body. Compare exogenous. [4]
endogenous attention
Also called voluntary attention. The voluntary direction of attention toward specific aspects of the environment, in accordance with our interests and goals. Compare exogenous attention. [14]
endogenous ligand
Any substance, produced within the body, that selectively binds to the type of receptor that is under study. Compare exogenous ligand. [4]
endogenous opioid
Any of a class of opium-like peptide transmitters that have been referred to as the body’s own narcotics. The three kinds are enkephalins, endorphins, and dynorphins. See Table 4.1. [4]
endorphin
One of the three kinds of endogenous opioids. Compare dynorphin and enkephalin. See Table 4.1. [4, 5]
endotherm
An animal whose body temperature is regulated chiefly by internal metabolic processes. Examples include mammals and birds. Compare ectotherm. [9]
enkephalin
One of the three kinds of endogenous opioids. Compare dynorphin and endorphin. See Table 4.1. [4]
enriched condition (EC)
Also called complex environment. An environment for laboratory rodents in which animals are group-housed with a wide variety of stimulus objects. See Figure 13.16. Compare impoverished condition and standard condition. [13]
entrainment
The process of synchronizing a biological rhythm to an environmental stimulus. See Figure 10.1. [10]
enzyme
A complicated protein whose action increases the probability of a specific chemical reaction. [App]
ependymal layer
See ventricular zone. [13]
epigenetic regulation
Changes in gene expression that are due to environmental effects rather than to changes in the nucleotide sequence of the gene. [11]
epigenetic transmission
The passage from one individual to another of changes in the expression of targeted genes, without modifications to the genes themselves. [9]
epigenetics
The study of factors that affect gene expression without making any changes in the nucleotide sequence of the genes themselves. [1, 13]
epilepsy
A brain disorder marked by major, sudden changes in the electrophysiological state of the brain that are referred to as seizures. See Figure 3.16. [3]
epinephrine
Also called adrenaline. A compound that acts both as a hormone (secreted by the adrenal medulla under the control of the sympathetic nervous system) and as a synaptic transmitter. See Tables 4.1, 8.1. [11]
episodic memory
Also called autobiographical memory. Memory of a particular incident or a particular time and place. Compare semantic memory. [13]
EPSP
See excitatory postsynaptic potential. [3]
equilibrium potential
The point at which the movement of ions across the cell membrane is balanced, as the electrostatic pressure pulling ions in one direction is offset by the diffusion force pushing them in the opposite direction. [3]
ERP
See event-related potential. [3, 14]
estradiol
The primary type of estrogen that is secreted by the ovary. Its formal name is 17-beta-estradiol. [8]
estrogen
Any of a class of steroid hormones, including estradiol, produced by female gonads. See Figure 8.13. [8]
estrus
The period during which female animals are sexually receptive. [8]
eukaryote
Any organism whose cells have the genetic material contained within a nuclear envelope. [App]
event-related potential (ERP)
Also called evoked potential. Averaged EEG recordings measuring brain responses to repeated presentations of a stimulus. Components of the ERP tend to be reliable because the background noise of the cortex has been averaged out. See Figures 3.15, 14.6. [3, 14]
evoked potential
See event-related potential. [3, 14]
evolution by natural selection
The Darwinian theory that evolution proceeds by differential success in reproduction.
evolutionary psychology
A field of study devoted to asking how natural selection has shaped behavior in humans and other animals. [1]
excitatory postsynaptic potential (EPSP)
A depolarizing potential in the postsynaptic neuron that is normally caused by synaptic excitation. EPSPs increase the probability that the postsynaptic neuron will fire an action potential. See Figure 3.9. Compare inhibitory postsynaptic potential. [3]
excitotoxicity
The property by which neurons die when overstimulated, as with large amounts of glutamate. [ASF 15.5]
executive function
A neural and cognitive system that helps develop plans of action and organizes the activities of other high-level processing systems. [14]
exocytosis
A cellular process that results in the release of a substance into the extracellular space. [4]
exogenous
Arising from outside the body. Compare endogenous. [4]
exogenous attention
Also called reflexive attention. The involuntary reorienting of attention toward a specific stimulus source, cued by an unexpected object or event. Compare endogenous attention. [14]
exogenous ligand
Any substance, originating from outside the body, that selectively binds to the type of receptor that is under study. Compare endogenous ligand. [4]
expression
See gene expression. [1, 13, App]
external ear
The part of the ear that we readily see (the pinna) and the canal that leads to the eardrum. See Figure 6.1.
extracellular compartment
The fluid space of the body that exists outside the cells. See Figure 9.7. Compare intracellular compartment. [9]
extracellular fluid
The fluid in the spaces between cells (interstitial fluid) Compare intracellular fluid. [3]
extraocular muscle
One of the muscles attached to the eyeball that control its position and movements. [7]
extrapyramidal system
A motor system that includes the basal ganglia and some closely related brainstem structures. Axons of this system pass into the spinal cord outside the pyramids of the medulla. Compare pyramidal system. [5]
extrastriate cortex
Visual cortex outside of the primary visual (striate) cortex. [7]

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F

face blindness
See prosopagnosia. [15]
facial feedback hypothesis
The idea that sensory feedback from our facial expressions can affect our mood. [11]
fat
See lipid. [9]
fat tissue
See adipose tissue. [9]
fatal familial insomnia
An inherited disorder in which humans sleep normally at the beginning of their life but in midlife stop sleeping and, 7–24 months later, die. See Box 10.1. [10]
fear conditioning
A form of classical conditioning in which fear comes to be associated with previously neutral stimuli. [11, 12]
feature search
A search for an item in which the target pops out right away, no matter how many distracters are present, because it possesses a unique attribute. Compare conjunction search. [14]
FEF
See frontal eye field. [14]
fetal alcohol syndrome
A disorder, including intellectual disability and characteristic facial abnormalities, that affects children exposed to too much alcohol (through maternal ingestion) during fetal development. [4]
fetus
A developing individual after the embryo stage. Humans are considered to be fetuses from 10 weeks after fertilization until birth. Compare embryo. [13]
fiber tracking
See DTI tractography. [15]
final common pathway
The motoneurons of the brain and spinal cord, so called because they receive and integrate all motor signals from the brain to direct movement. [5]
flavor
The sense of taste combined with the sense of smell. Compare taste. [6]
fluent aphasia
Also called Wernicke’s aphasia. A language impairment characterized by fluent, meaningless speech and little language comprehension. It is related to damage in Wernicke’s area. See Figure 15.8. Compare nonfluent aphasia. [15]
fMRI
See functional MRI. [2]
follicle
The structure of the ovary that contains an immature ovum (egg). [8, ASF 8.3]
follicle-stimulating hormone (FSH)
A gonadotropin, named for its actions on ovarian follicles. See Figure 8.13. [8, ASF 8.3]
forebrain
The frontmost division of the brain, which in the mature vertebrate contains the cerebral hemispheres, the thalamus, and the hypothalamus. See Figures 2.12, 13.24. Compare hindbrain and midbrain. [2, 13]
fornix
A fiber tract that extends from the hippocampus to the mammillary body. See Figures 2.14, 2.16. [2]
Fourier analysis
The mathematical decomposition of a complex pattern into a sum of sine waves. [6, ASF 7.2]
fourth ventricle
The passageway within the pons that receives cerebrospinal fluid from the third ventricle and releases it to surround the brain and spinal cord. See Figure 2.17. Compare lateral ventricle and third ventricle. [2]
fovea
The central portion of the retina, which is packed with the highest density of photoreceptors and is the center of our gaze. See Figure 7.1. [7]
fraternal birth order effect
A phenomenon in human populations, such that the more older biological brothers a boy has, the more likely he is to develop a homosexual orientation. [8]
free nerve ending
An axon that terminates in the skin and has no specialized cell associated with it. Free nerve endings detect pain and/or changes in temperature. See Figure 5.3. [5]
free-running
Referring to a rhythm of behavior shown by an animal deprived of external cues about time of day. See Figure 10.1. [10]
free will
The feeling that our conscious self is the author of our actions and decisions. [14]
frequency
The number of cycles per second in a sound wave, measured in hertz. See Box 6.1. [6]
frontal eye field (FEF)
An area in the frontal lobe of the brain that contains neurons important for establishing gaze in accordance with cognitive goals (top-down processes) rather than with any characteristics of stimuli (bottom-up processes). [14]
frontal lobe
The most anterior portion of the cerebral cortex. See Figure 2.10. Compare occipital lobe, parietal lobe, and temporal lobe. [2]
frontal plane
See coronal plane. [2]
FSH
See follicle-stimulating hormone. [8, ASF 8.3]
functional MRI (fMRI)
Magnetic resonance imaging that detects changes in blood flow and therefore identifies regions of the brain that are particularly active during a given task. See Figure 2.19. Compare positron emission tomography. [2]
functional tolerance
The form of drug tolerance that arises when repeated exposure to the drug causes receptors to be up-regulated or down-regulated. Compare metabolic tolerance. [4]
fundamental
The predominant frequency of an auditory tone. Compare harmonic. See Box 6.1. [6]
fusiform gyrus
A region on the inferior surface of the cortex, at the junction of the temporal and occipital lobes, that has been associated with recognition of faces. See Figure 15.5. [15]

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G

GABA
See gamma-aminobutyric acid. [4]
gamete
A sex cell (sperm or ovum) that contains only unpaired chromosomes and therefore has only half of the usual number of chromosomes. [8]
gamma-aminobutyric acid (GABA)
A widely distributed amino acid transmitter, the main inhibitory transmitter in the mammalian nervous system. See Table 4.1. [4]
ganglion (pl. ganglia)
A collection of nerve cell bodies outside the central nervous system. Compare nucleus (definition 1).
ganglion cell
Any of a class of cells in the retina whose axons form the optic nerve. See Figure 7.15. Compare amacrine cell, bipolar cell, and horizontal cell. [7]
gap junction
See electrical synapse. [ASF 3.1]
gas neurotransmitter
A neurotransmitter that is a soluble gas. Examples include nitric oxide and carbon monoxide. Usually gas neurotransmitters act, in a retrograde fashion, on presynaptic neurons. See Table 4.1. Compare amine neurotransmitter, amino acid neurotransmitter, and peptide neurotransmitter. [4]
gel electrophoresis
A method of separating molecules of differing size or electrical charge by forcing them to flow through a gel. See Appendix Figure A.3. [App]
gene
A length of DNA that encodes the information for constructing a particular protein. [App]
gene amplification
See polymerase chain reaction. [App]
gene expression
The turning on or off of specific genes. The process by which a cell makes an mRNA transcript of a particular gene. [1, App]
general anesthetic
A drug that renders an individual unconscious. [10]
generator potential
A local change in the resting potential of a receptor cell in response to stimuli, which may initiate an action potential. [5]
genital tubercle
In the early fetus, a “bump” between the legs that can develop into either a clitoris or a penis. [8]
genome
See genotype. [App]
genotype
Also called genome. All the genetic information that one specific individual has inherited. Compare phenotype. [13, App]
GH
See growth hormone. [8, ASF 8.3]
ghrelin
A peptide hormone produced and released by the gut. See Figure 9.15. Compare PYY3-36. [9]
glial cells
Also called glia. Nonneuronal brain cells that provide structural, nutritional, and other types of support to the brain. See Figure 2.5. [2]
global aphasia
The total loss of ability to understand language, or to speak, read, or write. See Figure 15.8. [15]
globus pallidus
One of the basal ganglia. See Figure 2.14. [2]
glomerulus (pl. glomeruli)
A complex arbor of dendrites from a group of olfactory cells. [6]
glucagon
A pancreatic hormone that converts glycogen to glucose and thus increases blood glucose. Compare insulin. [9]
glucocorticoid
Any of a class of steroid hormones, released by the adrenal cortex, that affect carbohydrate metabolism and inflammation.
glucodetector
A specialized type of liver cell that detects and informs the nervous system about levels of circulating glucose. [9]
glucose
An important sugar molecule used by the body and brain for energy. [9]
glutamate
An amino acid transmitter, the most common excitatory transmitter. See Table 4.1. [4, 13]
glutamate hypothesis
The idea that schizophrenia may be caused, in part, by understimulation of glutamate receptors. [12]
glutamatergic
Referring to cells that use glutamate as their synaptic transmitter.
glycine
An amino acid transmitter, often inhibitory. See Table 4.1.
glycogen
A complex carbohydrate made by the combining of glucose molecules for a short-term store of energy. [9]
GnRH
See gonadotropin-releasing hormone. [8]
Golgi stain
A tissue stain that completely fills a small proportion of neurons with a dark, silver-based precipitate. See Box 2.1. [2]
Golgi tendon organ
A type of receptor found within tendons that sends impulses to the central nervous system when a muscle contracts. See Figure 5.20. Compare muscle spindle. [5]
gonad
Any of the sexual organs (ovaries in females, testes in males) that produce gametes for reproduction. See Figure 8.1. [8]
gonadotropin
An anterior pituitary hormone that selectively stimulates the cells of the gonads to produce sex steroids and gametes. See luteinizing hormone and follicle-stimulating hormone. [8, ASF 8.3]
gonadotropin-releasing hormone (GnRH)
A hypothalamic hormone that controls the release of luteinizing hormone and follicle-stimulating hormone from the pituitary. See Figure 8.13. [8]
grammar
All of the rules for usage of a particular language. [15]
grand mal seizure
A type of generalized epileptic seizure in which nerve cells fire in high-frequency bursts, usually accompanied by involuntary rhythmic contractions of the body. See Figure 3.16. Compare petit mal seizure. [3]
gray matter
Areas of the brain that are dominated by cell bodies and are devoid of myelin. Gray matter mostly receives and processes information. See Figure 2.11. Compare white matter. [2]
gross neuroanatomy
Anatomical features of the nervous system that are apparent to the naked eye. [2]
growth hormone (GH)
Also called somatotropin or somatotropic hormone. A tropic hormone, secreted by the anterior pituitary, that promotes the growth of cells and tissues. [8, ASF 8.3]
guevedoces
Literally “eggs at 12” (in Spanish). A nickname for individuals who are raised as girls but at puberty change appearance and begin behaving as boys. [8]
gustatory system
The sensory system that detects taste. See Figure 6.18. [6]
gyrus (pl. gyri)
A ridged or raised portion of a convoluted brain surface. Compare sulcus. [2]

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H

habituation
A form of nonassociative learning in which an organism becomes less responsive following repeated presentations of a stimulus. See Figure 13.19. [13]
hair cell
One of the receptor cells for hearing in the cochlea, named for the stereocilia that protrude from the top of the cell and transduce vibrational energy in the cochlea into neural activity. See Figures 6.1, 6.3. [6]
hallucinogen
A drug that alters sensory perception and produces peculiar experiences. Compare dissociative. [4]
hard problem of consciousness
Under-standing the brain processes that produce people’s subjective experiences of their conscious perceptions—that is, their qualia. Compare easy problem of consciousness. [14]
harmonic
A multiple of a particular frequency called the fundamental. See Box 6.1. [6]
health psychology
Also called behavioral medicine. A field of study that focuses on the influence of psychological influences on health and disease-related processesy. [11]
Hebbian synapse
A synapse that is strengthened when it successfully drives the postsynaptic cell. [13, ASF 13.4]
hemiparesis
Weakness of one side of the body. Compare hemiplegia. [15]
hemiplegia
Paralysis of one side of the body. Compare hemiparesis. [15]
hemispatial neglect
Failure to pay any attention to objects presented to one side of the body. [14]
hermaphrodite
An individual possessing the reproductive organs of both sexes, either simultaneously or at different points in time. [ASF 8.5]
heroin
Diacetylmorphine, an artificially modified, very potent form of morphine. [4]
hertz (Hz)
Cycles per second, as of an auditory stimulus. Hertz is a measure of frequency. See Box 6.1. [6]
hindbrain
The rear division of the brain, which in the mature vertebrate contains the cerebellum, pons, and medulla. See Figures 2.12, 13.24. Compare forebrain and midbrain. [2, 13]
hippocampus (pl. hippocampi)
A medial temporal lobe structure that is important for spatial cognition, learning and memory. See Figures 2.14, 13.1, 13.21. [2, 13]
histology
The study of tissue structure.
homeostasis
The active process of keeping a particular physiological parameter relatively constant. [9]
horizontal cell
A specialized retinal cell that contacts both photoreceptors and bipolar cells. Compare amacrine cell and ganglion cell. [7]
horizontal plane
The plane that divides the body or brain into upper and lower parts. See Box 2.2. Compare coronal plane and sagittal plane. [2]
hormone
A chemical, usually secreted by an endocrine gland, that is conveyed by the bloodstream and regulates target organs or tissues. See Table 8.1. [8]
horseradish peroxidase (HRP)
An enzymatic label, originating in horseradish and other plants, that is used to determine the cells of origin of a particular set of axons. See Box 2.1. [2]
HRP
See horseradish peroxidase. [2]
hue
One of three basic dimensions of light perception, varying through the spectrum from blue to red. Compare brightness and saturation. [7]
hunger
The internal state of an animal seeking food. Compare satiety. [9]
huntingtin
A protein produced by a gene (called HTT) that, when containing too many trinucleotide repeats, results in Huntington’s disease in a carrier. [ASF 5.5]
Huntington’s disease
A genetic disorder, with onset in middle age, in which the destruction of basal ganglia results in a syndrome of abrupt, involuntary writhing movements and changes in mental functioning. Compare Parkinson’s disease. [5]
hybridization
The process by which one string of nucleotides becomes linked to a complementary series of nucleotides. [App]
hyperpolarization
An increase in membrane potential (the interior of the neuron becomes even more negative). See Figure 3.5. Compare depolarization. [3]
hypertonic
Referring to a solution with a higher concentration of salt than that found in interstitial fluid and blood plasma (more than about 0.9% salt). Compare hypotonic and isotonic. [9]
hypocretin
See orexin. [9, 10]
hypofrontality hypothesis
The idea that schizophrenia may reflect underactivation of the frontal lobes. [12]
hypothalamic-pituitary portal system
An elaborate bed of blood vessels leading from the hypothalamus to the anterior pituitary. [8]
hypothalamus
Part of the diencephalon, lying ventral to the thalamus. See Figures 2.12, 2.14, 2.16. [2]
hypotonic
Referring to a solution with a lower concentration of salt than that found in interstitial fluid and blood plasma (less than about 0.9% salt). Compare hypertonic and isotonic. [9]
hypovolemic thirst
A desire to ingest fluids that is stimulated by a reduction in volume of the extracellular fluid. Compare osmotic thirst. [9]
Hz
See hertz. [6]

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I

IC
See impoverished condition. [13]
ICC
See immunocytochemistry. [2, 8, App]
iconic memory
See sensory buffer. [13]
IEG
See immediate early gene. [2]
IHC
See inner hair cell. [6]
immediate early gene (IEG)
A gene that shows rapid but temporary increases in expression in cells that have become activated. See Box 2.1. [2]
immunocytochemistry (ICC)
A method for detecting a particular protein in tissues in which an antibody recognizes and binds to the protein and then chemical methods are used to leave a visible reaction product around each antibody. See Boxes 2.1, 8.1. [2, 8, App]
immunoglobulin
See antibody. [ASF 11.4, App]
impoverished condition (IC)
Also called isolated condition. An environment for laboratory rodents in which each animal is housed singly in a small cage without complex stimuli. See Figure 13.16. Compare enriched condition and standard condition. [13]
in situ hybridization
A method for detecting particular RNA transcripts in tissue sections by providing a nucleotide probe that is complementary to, and will therefore hybridize with, the transcript of interest. See Boxes 2.1, 8.1; Appendix Figure A.4. [2, 8, App]
in vitro
Literally “in glass” (in Latin). Usually, in a laboratory dish; outside the body.
inattentional blindness
The failure to perceive nonattended stimuli that seem so obvious as to be impossible to miss. [14]
incus
Latin for “anvil.” A middle-ear bone situated between the malleus (attached to the tympanic membrane) and the stapes (attached to the cochlea). It is one of the three ossicles that conduct sound across the middle ear. See Figure 6.1. [6]
independent variable
The factor that is manipulated by an experimenter. Compare dependent variable. [1]
indifferent gonads
The undifferentiated gonads of the early mammalian fetus, which will eventually develop into either testes or ovaries. See Figure 8.24. See also gonad. [8]
indoleamines
A class of monoamines that serve as neurotransmitters, including serotonin and melatonin. See Table 4.1.
inferior
In anatomy, below. See Box 2.2. Compare superior. [2]
inferior colliculi (sing. colliculus)
Paired gray matter structures of the dorsal midbrain that process auditory information. See Figure 2.16. Compare superior colliculi. [2, 6]
infradian
Referring to a rhythmic biological event with a period longer than a day. Compare ultradian. [10]
infrasound
Very low frequency sound; in general, below the threshold for human hearing, at about 20 Hz. Compare ultrasound. [6]
infundibulum
See pituitary stalk. [8]
inhibition of return
The phenomenon, observed in peripheral spatial cuing tasks when the interval between cue and target stimulus is 200 milliseconds or more, in which the detection of stimuli at the former location of the cue is increasingly impaired. [14]
inhibitory postsynaptic potential (IPSP)
A hyperpolarizing potential in the postsynaptic neuron. IPSPs decrease the probability that the postsynaptic neuron will fire an action potential. See Figure 3.9. Compare excitatory postsynaptic potential. [3]
inner ear
The cochlea and vestibular apparatus. See Figure 6.1. [6]
inner hair cell (IHC)
One of the two types of receptor cells for hearing in the cochlea. Compared with outer hair cells, IHCs are positioned closer to the central axis of the coiled cochlea. See Figure 6.1. [6]
innervate
To provide neural input to. [2]
input zone
The part of a neuron that receives information from other neurons or from specialized sensory structures. This zone usually corresponds to the cell’s dendrites. See Figures 2.1, 2.3. Compare conduction zone, integration zone, and output zone. [2]
instrumental conditioning
Also called operant conditioning. A form of associative learning in which the likelihood that an act (instrumental response) will be performed depends on the consequences (reinforcing stimuli) that follow it. Compare classical conditioning. [13]
insula
A region of cortex lying below the surface, within the lateral sulcus, of the frontal, temporal, and parietal lobes. [4]
insulin
A pancreatic hormone that lowers blood glucose, promotes energy storage, and facilitates glucose utilization by cells. Compare glucagon. [9]
integration zone
The part of a neuron that initiates neural electrical activity. This zone usually corresponds to the neuron’s cell body. See Figures 2.1, 2.3. Compare conduction zone, input zone, and output zone. [2]
intensity
See amplitude. [6]
intensity difference
A perceived difference in loudness between the two ears, which the nervous system can use to localize a sound source. Compare latency difference. [6]
intermale aggression
Aggression between males of the same species. [11]
interneuron
A nerve cell that is neither a sensory neuron nor a motoneuron; interneurons receive input from and send output to other neurons. Compare motoneuron and sensory neuron. [2]
intersex
Referring to an individual with atypical genital development and sexual differentiation that generally resembles a form intermediate between typical male and typical female genitalia. [8]
intracellular compartment
The fluid space of the body that is contained within cells. See Figure 9.7. Compare extracellular compartment. [9]
intracellular fluid
Also called cytoplasm. The watery solution found within cells. Compare extracellullar fluid. [3]
intrafusal fiber
Any of the small muscle fibers that lie within each muscle spindle. See Figure 5.20. [5]
intraparietal sulcus (IPS)
A region in the human parietal lobe, homologous to the monkey lateral intraparietal area, that is especially involved in voluntary, top-down control of attention. [14]
intrinsic activity
See efficacy. [4]
intromission
Insertion of the penis into the vagina during copulation. [8]
inverse agonist
A substance that binds to a receptor and causes it to do the opposite of what the naturally occurring transmitter does.
ion
An atom or molecule that has acquired an electrical charge by gaining or losing one or more electrons. [3]
ion channel
A pore in the cell membrane that permits the passage of certain ions through the membrane when the channels are open. See Figure 3.2. [3]
ionotropic receptor
Also called ligand-gated ion channel. A receptor protein containing an ion channel that opens when the receptor is bound by an agonist. See Figure 4.2. Compare metabotropic receptor. [4]
IPS
See intraparietal sulcus. [14]
ipsilateral
In anatomy, pertaining to a location on the same side of the body. See Box 2.2. Compare contralateral. [2]
IPSP
See inhibitory postsynaptic potential. [3]
iris (pl. irides)
The circular structure of the eye that provides an opening to form the pupil. See Figure 7.1. [7]
isocortex
See neocortex.
isolated brain
Also called encéphale isolé. An experimental preparation in which an animal’s brainstem has been separated from the spinal cord by a cut below the medulla.See Figure 10.17. Compare isolated forebrain. [10]
isolated condition
See impoverished condition. [13]
isolated forebrain
Also called cerveau isolé. An experimental preparation in which an animal’s nervous system has been cut in the upper midbrain, dividing the forebrain from the brainstem. See Figure 10.17. Compare isolated brain. [10]
isotonic
Referring to a solution with a concentration of salt that is the same as that found in interstitial fluid and blood plasma (about 0.9% salt). Compare hypertonic and hypotonic. [9]

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K

K complex
A sharp, negative EEG potential that is seen in stage 2 sleep. [10]
kcal
See kilocalorie. [ASF 9.1]
ketamine
A dissociative anesthetic drug, similar to PCP, that acts as an NMDA receptor antagonist. [12]
ketone
A compound, liberated by the breakdown of body fats and proteins, that is a metabolic fuel source. [9]
kilocalorie (kcal)
A measure of energy commonly applied to food; formally defined as the quantity of heat required to raise the temperature of 1 kilogram of water by 1°C. [ASF 9.1]
Klüver-Bucy syndrome
A condition, brought about by bilateral amygdala damage, that is characterized by dramatic emotional changes including reduction in fear and anxiety. [11]
knee jerk reflex
A variant of the stretch reflex in which stretching of the tendon beneath the knee leads to an upward kick of the leg. See Figure 3.14. [3]
knockout organism
An individual in which a particular gene has been disabled by an experimenter. See Box 8.1. [8]
Korsakoff’s syndrome
A memory disorder, caused by thiamine deficiency, that is generally associated with chronic alcoholism. [13]

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L

l-dopa
The immediate precursor of the transmitter dopamine. It is known to markedly reduce symptoms in patients with Parkinson’s, decreasing tremors and increasing the speed of movements. [ASF 5.5]
labeled lines
The concept that each nerve input to the brain reports only a particular type of information. [5]
lamellated corpuscle
See Pacinian corpuscle. [5]
language
Communication in which arbitrary sounds or symbols are arranged according to a grammar in order to convey an almost limitless variety of concepts. [15]
latency difference
A difference between the two ears in the time of arrival of a sound, which the nervous system can use to localize a sound source. Compare intensity difference. [6]
lateral
In anatomy, toward one side. See Box 2.2. Compare medial. [2]
lateral geniculate nucleus (LGN)
The part of the thalamus that receives information from the optic tract and sends it to visual areas in the occipital cortex. [7]
lateral hypothalamus (LH)
A hypothalamic region involved in the control of appetite and other functions. See Figure 9.12. [9]
lateral inhibition
The phenomenon by which interconnected neurons inhibit their neighbors, producing contrast at the edges of regions. See Figure 7.15. [7]
lateral intraparietal area (LIP)
A region in the monkey parietal lobe, homologous to the human intraparietal sulcus, that is especially involved in voluntary, top-down control of attention. [14]
lateral sulcus
See Sylvian fissure. [2]
lateral tegmental area
A brainstem region that provides some of the norepinephrine-containing projections of the brain. [4]
lateral ventricle
A complex C-shaped lateral portion of the ventricular system within each hemisphere of the brain. See Figures 2.15, 2.17. Compare fourth ventricle and third ventricle. [2]
lateralization
The tendency for the right and left halves of a system to differ from one another.
LD50
Lethal dose 50%; the dose of a drug at which half the treated animals will die. See Figure 4.6. Compare ED50.
learned helplessness
A learning paradigm in which individuals are subjected to inescapable, unpleasant conditions. [12]
learning
The process of acquiring new and relatively enduring information, behavior patterns, or abilities, characterized by modifications of behavior as a result of practice, study, or experience. [13]
lens
A structure in the eye that helps focus an image on the retina. See Figure 7.1. [7]
leptin
A peptide hormone released by fat cells. [9]
lesion momentum
The phenomenon in which the brain is impaired more by a lesion that develops quickly than by a lesion that develops slowly. [15]
levels of analysis
The scope of experimental approaches. A scientist may try to understand behavior by monitoring molecules, nerve cells, brain regions, or social environments or using some combination of these levels of analysis. [1]
LGN
See lateral geniculate nucleus. [7]
LH
1. See lateral hypothalamus. [9] 2. See luteinizing hormone. [8, ASF 8.3]
lie detector
See polygraph. [11]
ligand
A substance that binds to receptor molecules, such as a neurotransmitter or drug that binds postsynaptic receptors.[3, 4]
ligand-gated ion channel
See ionotropic receptor. [4]
limbic system
A loosely defined, widespread group of brain nuclei that innervate each other and form a network. These nuclei are implicated in emotions. See Figure 2.14. [2, 11]
LIP
See lateral intraparietal area. [14]
lipid
A large molecule (commonly called a fat) that consists of fatty acids and glycerol. Lipids are insoluble in water. [9]
liposuction
The surgical removal of fat tissue. [9]
lithium
An element that, administered to patients, often relieves the symptoms of bipolar disorder. [12]
lobotomy
The surgical separation of a portion of the frontal lobes from the rest of the brain, once used as a treatment for schizophrenia and many other ailments. [12]
local anesthetic
A drug, such as procaine or lidocaine, that blocks sodium channels to stop neural transmission in pain fibers.
local potential
An electrical potential that is initiated by stimulation at a specific site, which is a graded response that spreads passively across the cell membrane, decreasing in strength with time and distance.[3]
localization of function
The concept that different brain regions specialize in specific behaviors. [1]
locus coeruleus
A small nucleus in the brainstem whose neurons produce norepinephrine and modulate large areas of the forebrain. Compare substantia nigra. [4, 10]
long-term memory (LTM)
An enduring form of memory that lasts days, weeks, months, or years and has a very large capacity. Compare sensory buffer and short-term memory. See Figure 13.13. [13]
long-term potentiation (LTP)
A stable and enduring increase in the effectiveness of synapses following repeated strong stimulation. See Figures 13.21, 13.22. [13]
lordosis
A female receptive posture in four-legged animals in which the hindquarters are raised and the tail is turned to one side, facilitating intromission by the male. See Figures 8.17, 8.20. [8]
Lou Gehrig’s disease
See amyotrophic lateral sclerosis. [ASF 5.5]
LSD
Also called acid. Lysergic acid diethylamide, a hallucinogenic drug. [4]
LTM
See long-term memory. [13]
LTP
See long-term potentiation. [13]
lumbar
Referring to the five spinal segments that make up the upper part of the lower back. See Figures 2.8, 2.9. Compare cervical, thoracic, sacral, and coccygeal. [2]
luteinizing hormone (LH)
A gonadotropin, named for its stimulatory effects on the ovarian corpora lutea. See Figure 8.13. [8, ASF 8.3]
lysergic acid diethylamide
See LSD. [4]

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M

M1
See primary motor cortex. [5]
magnetic resonance imaging (MRI)
A noninvasive brain imaging technology that uses magnetism and radio-frequency energy to create images of the gross structure of the living brain. See Figures 1.5, 2.19. Compare computerized axial tomography. [2]
magnetoencephalography (MEG)
A noninvasive brain-imaging technology that creates maps of brain activity during cognitive tasks by measuring the tiny magnetic fields produced by active neurons. Compare transcranial magnetic stimulation. [2]
malleus
Latin for “hammer.” A middle-ear bone that is connected to the tympanic membrane. It is one of the three ossicles that conduct sound across the middle ear. See Figure 6.1. Compare incus and stapes. [6]
mammillary body
One of a pair of limbic system structures that are connected to the hippocampus. See Figure 2.14. [13]
MAO
See monoamine oxidase. [4, ASF 4.1, 12]
maternal aggression
Aggression of a mother defending her nest or offspring. [11]
MD
See muscular dystrophy. [ASF 5.5]
MDMA
Also called Ecstasy. 3,4-Methylenedioxymethamphetamine, a drug of abuse. [4]
medial
In anatomy, toward the middle. See Box 2.2. Compare lateral. [2]
medial amygdala
A portion of the amygdala that receives olfactory and pheromonal information. [8, 11]
medial forebrain bundle
A collection of axons traveling in the midline region of the forebrain. See Figure 4.17. [11]
medial geniculate nucleus
Either of two nuclei—left and right—in the thalamus that receive input from the inferior colliculi and send output to the auditory cortex. See Figure 6.6. [6]
medial preoptic area (mPOA)
A region of the anterior hypothalamus implicated in the control of many behaviors, including sexual behavior, gonadotropin secretion, and thermoregulation. [8]
median eminence
A midline feature on the base of the brain that marks the point at which the pituitary stalk exits the hypothalamus to connect to the pituitary. The median eminence contains elements of the hypothalamic-pituitary portal system. See Figure 8.12. [8]
medulla
The posterior part of the hindbrain, continuous with the spinal cord. See Figures 2.12, 2.16. [2]
MEG
See magnetoencephalography. [2]
Meissner’s corpuscle
Also called tactile corpuscle. A skin receptor cell type that detects light touch, responding especially to changes in stimuli. See Figures 5.3, 5.4. Compare Merkel’s disc, Pacinian corpuscle, and Ruffini corpuscle. [5]
melanopsin
A photopigment found in those retinal ganglion cells that project to the suprachiasmatic nucleus. See Figure 10.5. [10]
melatonin
An amine hormone that is secreted by the pineal gland at night, thereby signaling day length to the brain. See Table 4.1. [10, ASF 8.1]
memory
1. The capability to learn and neurally encode information, consolidate the information for longer term storage, and retrieve or reactivate the consolidated memory at a later time. 2. The specific information that is stored in the brain. [13]
memory trace
A persistent change in the brain that reflects the storage of memory. [13]
meninges
The three protective membranes—dura mater, pia mater, and arachnoid—that surround the brain and spinal cord. See Figure 2.8. [2]
meningioma
A noninvasive tumor of the meninges. [2]
meningitis
An acute inflammation of the meninges, usually caused by a viral or bacterial infection. [2]
Merkel’s disc
A skin receptor cell type that detects light touch, responding especially to edges and isolated points on a surface. See Figures 5.3, 5.4. Compare Meissner’s corpuscle, Pacinian corpuscle, and Ruffini corpuscle. [5]
message
See messenger RNA. [App]
messenger RNA (mRNA)
Also called transcript or message. A strand of RNA that carries the code of a section of a DNA strand to the cytoplasm. [App]
meta-analysis
A type of quantitative review of a field of research, in which the results of multiple previous studies are combined in order to identify overall patterns that are consistent across studies. [12]
metabolic tolerance
The form of drug tolerance that arises when repeated exposure to the drug causes the metabolic machinery of the body to become more efficient at clearing the drug. Compare functional tolerance. [4]
metabolism
The breakdown of complex molecules into smaller molecules. [ASF 9.1]
metabotropic receptor
A receptor protein that does not contain ion channels but may, when activated, use a second- messenger system to open nearby ion channels or to produce other cellular effects. See Figure 4.2. Compare ionotropic receptor. [4]
methylation
A chemical modification of DNA that does not affect the nucleotide sequence of a gene but makes that gene less likely to be expressed. [13]
microelectrode
An especially small electrode used to record electrical potentials in living cells. [3]
microglial cells
Also called microglia. Extremely small, motile glial cells that remove cellular debris from injured or dead cells. [2]
midbrain
The middle division of the brain. See Figures 2.12, 13.24. Compare forebrain and hindbrain. [2, 13]
middle canal
See scala media. See Figure 6.1.
middle cerebral artery
Either of two large arteries, arising from the carotid arteries, that provide blood to most of the forebrain. Compare anterior cerebral artery and posterior cerebral artery. [ASF 2.1]
middle ear
The cavity between the tympanic membrane and the cochlea. See Figure 6.1. [6]
milk letdown reflex
The reflexive release of milk by the mammary glands of a nursing female in response to suckling or to stimuli associated with suckling. See Figure 8.9. [8]
millivolt (mV)
A thousandth of a volt. [3]
mirror neuron
A neuron that is active both when an individual makes a particular movement and when that individual sees another individual make the same movement. [5]
mitochondrion (pl. mitochondria)
A cellular organelle that provides metabolic energy for the cell’s processes. See Figure 2.4. [2]
mitosis
The process of division of somatic cells that involves duplication of DNA. [13]
monaural
Pertaining to one ear. Compare binaural.
monoamine hormone
See amine hormone. [8]
monoamine oxidase (MAO)
An enzyme that breaks down monoamine neurotransmitters, thereby inactivating them. [4, 12, ASF 4.1]
monocular deprivation
Depriving one eye of form vision. Compare binocular deprivation. [ASF 13.4]
monopolar neuron
See unipolar neuron. [2]
monozygotic
Referring to twins derived from a single fertilized egg (identical twins). Such individuals share an identical set of genes. Compare dizygotic. [12]
morpheme
The smallest grammatical unit of a language; a word or meaningful part of a word. [15]
morphine
An opiate compound derived from the poppy flower. [4]
motion sickness
The experience of nausea brought on by unnatural passive movement, as may occur in a car or boat. [6]
motivation
The psychological process that induces or sustains a particular behavior. [9]
motoneuron
Also called motor neuron. A neuron that transmits neural messages to muscles (or glands). See Figure 5.19. Compare interneuron and sensory neuron. [2, 5]
motor nerve
A nerve that transmits information from the central nervous system to the muscles and glands. Compare sensory nerve. [2]
motor neuron
See motoneuron. [2]
motor plan
Also called motor program. A plan for a series of muscular contractions, established in the nervous system prior to its execution. [5]
motor theory of language
The theory that speech is perceived using the same left-hemisphere mechanisms as are used to produce the complex movements that go into speech. Compare connectionist model of aphasia. [15]
motor unit
A single motor axon and all the muscle fibers that it innervates. [5]
movement
A single relocation of a body part, usually resulting from a brief muscle contraction. It is less complex than an act. [5]
mPOA
See medial preoptic area. [8]
MRI
See magnetic resonance imaging. [2]
mRNA
See messenger RNA. [App]
müllerian duct
A duct system in the embryo that will develop into female reproductive structures (oviducts, uterus, and upper vagina) if androgens are not present. See Figure 8.24. Compare wolffian duct. [8]
müllerian regression hormone
See anti-müllerian hormone. [8]
multiple sclerosis (MS)
Literally “many scars.” A disorder characterized by the widespread degeneration of myelin. [2, 3, ASF 13.3]
multipolar neuron
A nerve cell that has many dendrites and a single axon. See Figure 2.3. Compare bipolar neuron and unipolar neuron. [2]
multisensory
See polymodal. [ASF 6.3]
muscarinic
Referring to cholinergic receptors that respond to the chemical muscarine as well as to acetylcholine. Muscarinic receptors mediate chiefly the inhibitory activities of acetylcholine. Compare nicotinic.
muscle fiber
Large, cylindrical cells, making up most of a muscle, that can contract in response to neurotransmitter released from a motoneuron. See Figures 5.19, 5.20. See intrafusal fiber.
muscle spindle
A muscle receptor that lies parallel to a muscle and sends impulses to the central nervous system when the muscle is stretched. See Figure 5.19. Compare Golgi tendon organ. [5]
muscular dystrophy (MD)
A disease that leads to degeneration of and functional changes in muscles. [ASF 5.5]
musth
An annual period of heightened aggressiveness and sexual activity in male elephants. [ASF 8.6]
mV
See millivolt. [3]
myasthenia gravis
A disorder characterized by a profound weakness of skeletal muscles. It is caused by a loss of acetylcholine receptors. [ASF 5.5]
myelin
The fatty insulation around an axon, formed by glial cells. This sheath boosts the speed at which action potentials are conducted. See Figures 2.5, 3.8. [2, 3]
myelination
The process by which myelin sheaths develop around axons. See Figure 2.5. [ASF 13.3]
myopia
Nearsightedness; the inability to focus the retinal image of objects that are far away. [7]

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N

N1 effect
See auditory N1 effect. [14]
naloxone
A potent antagonist of opiates that is often administered to people who have taken drug overdoses. It binds to receptors for endogenous opioids. [5]
narcolepsy
A disorder that involves frequent, intense episodes of sleep, which last from 5 to 30 minutes and can occur anytime during the usual waking hours. [10]
NE
See norepinephrine. [4, 11]
negative correlation
A covariation of two measures in which one of the two usually goes up when the other goes down (and vice versa). Compare positive correlation. [1]
negative feedback
The property by which some of the output of a system feeds back to reduce the effect of input signals. [8, 9]
negative symptom
In psychiatry, an abnormality that reflects insufficient functioning. Examples include emotional and social withdrawal, and blunted affect. Compare positive symptom. [12]
neocortex
Also called isocortex or simply cortex. Cerebral cortex that is made up of six distinct layers.
neonatal
Referring to newborns. [8]
nerve
A collection of axons bundled together outside of the central nervous system. See Figures 2.6, 2.7. Compare tract. [2]
nerve cell
See neuron. [1, 2]
nerve fiber
See axon. [2]
neural chain
A simple kind of neural circuit in which neurons are attached linearly, end-to-end. [ASF 3.2]
neural groove
In the developing embryo, the groove between the neural folds. See Figure 13.24.
neural plasticity
See neuroplasticity. [1, 2, 13]
neural tube
An embryonic structure with subdivisions that correspond to the future forebrain, midbrain, and hindbrain. The cavity of this tube will include the cerebral ventricles and the passages that connect them. See Figure 13.24. [2, 13]
neuroeconomics
The study of brain mechanisms at work during economic decision making. [1, 14]
neuroendocrine cell
A neuron that releases hormones into local or systemic circulation. [8]
neurofibrillary tangle
An abnormal whorl of neurofilaments within nerve cells that is seen in Alzheimer’s disease. See Figure 13.34. [13]
neurogenesis
The mitotic division of nonneuronal cells to produce neurons. See Figure 13.25. [13]
neuroleptic
See antipsychotic. [4, 12]
neuromuscular junction
The region where the motoneuron terminal and the adjoining muscle fiber meet. It is the point where the nerve transmits its message to the muscle fiber. [5]
neuron
Also called nerve cell. The basic unit of the nervous system, each composed of receptive extensions called dendrites, an integrating cell body, a conducting axon, and a transmitting axon terminal. See Figures 2.2, 2.3. [1, 2]
neuron doctrine
The hypothesis that the brain is composed of separate cells that are distinct structurally, metabolically, and functionally.
neuropathic pain
Pain that persists long after the injury that started it has healed. [5]
neuropeptide
See peptide neurotransmitter. [4]
neurophysiology
The study of the life processes of neurons. [3]
neuroplasticity
Also called neural plasticity. The ability of the nervous system to change in response to experience or the environment. [1, 2, 13]
neuroscience
The scientific study of the nervous system. [1]
neurotransmitter
Also called simply transmitter, synaptic transmitter, or chemical transmitter. A signaling chemical, released by a presynaptic neuron, that diffuses across the synaptic cleft to alter the functioning of the postsynaptic neuron. See Figure 3.11; Table 4.1. [2, 3, 4]
neurotransmitter receptor
Also called simply receptor. A specialized protein, often embedded in the cell membrane, that selectively senses and reacts to molecules of a corresponding neurotransmitter or hormone. [2, 3, 4]
neurotrophic factor
Also called simply trophic factor. A target-derived chemical that acts as if it “feeds” certain neurons to help them survive. See Figure 13.28. [13]
nicotine
A compound found in plants, including tobacco, that acts as an agonist on a large class of cholinergic receptors. [4]
nicotinic
Referring to cholinergic receptors that respond to nicotine as well as to acetylcholine. Nicotinic receptors mediate chiefly the excitatory activities of acetylcholine, including at the neuromuscular junction. Compare muscarinic.
night terror
A sudden arousal from stage 3 sleep that is marked by intense fear and autonomic activation. Compare nightmare. [10]
nightmare
A long, frightening dream that awakens the sleeper from REM sleep. Compare night terror. [10]
Nissl stain
A tissue stain that outlines all cell bodies because the dyes are attracted to RNA, which encircles the nucleus. See Box 2.1. [2]
NMDA receptor
A glutamate receptor that also binds the glutamate agonist NMDA (N-methyl-d-aspartate) and that is both ligand-gated and voltage-sensitive. Compare AMPA receptor. [13, ASF 4.2]
nociceptor
A receptor that responds to stimuli that produce tissue damage or pose the threat of damage. [5]
nocturnal
Active during the dark periods of the daily cycle. Compare diurnal. [10]
node of Ranvier
A gap between successive segments of the myelin sheath where the axon membrane is exposed. See Figures 2.5, 3.8. [2, 3]
nonassociative learning
A type of learning in which presentation of a particular stimulus alters the strength or probability of a response. It includes habituation and sensitization. See Figure 13.19. Compare associative learning. [13]
noncompetitive ligand
A drug that affects a transmitter receptor while binding at a site other than that bound by the endogenous ligand.
nondeclarative memory
Also called procedural memory. A memory that is shown by performance rather than by conscious recollection. See Figures 13.4, 13.12. Compare declarative memory. [13]
nonfluent aphasia
Also called Broca’s aphasia. A language impairment characterized by difficulty with speech production but not with language comprehension. It is related to damage in Broca’s area. See Figure 15.8. Compare fluent aphasia. [15]
nonprimary motor cortex
Frontal lobe regions adjacent to the primary motor cortex that contribute to motor control and modulate the activity of the primary motor cortex. See Figure 5.25. [5]
nonprimary sensory cortex
Also called secondary sensory cortex. For a given sensory modality, the cortical regions receiving direct projections from primary sensory cortex for that modality. Compare primary sensory cortex. [5]
non-REM sleep
Sleep, divided into stages 1–3, that is defined by the presence of distinctive EEG activity that differs from that seen in REM sleep. [10]
noradrenaline
See norepinephrine. [4, 11]
noradrenergic
Referring to cells using norepinephrine (noradrenaline) as a transmitter. [4]
norepinephrine (NE)
Also called noradrenaline. A neurotransmitter that is produced and released by sympathetic postganglionic neurons to accelerate organ activity. It is also produced in the brainstem and found in projections throughout the brain. See Figure 4.4; Table 4.1. [4, 11]
Northern blot
A method of detecting a particular RNA transcript in a tissue or organ by separating RNA from that source with gel electrophoresis, blotting the separated RNA molecules onto nitrocellulose, and then using a nucleotide probe to hybridize with, and highlight, the transcript of interest. Compare Southern blot and Western blot. [App]
NPY neuron
A neuron, involved in the hypothalamic appetite control system, that produces both neuropeptide Y and agouti-related peptide. Compare POMC neuron. [9]
NST
See nucleus of the solitary tract. [9]
nucleotide
A portion of a DNA or RNA molecule that is composed of a single base and the adjoining sugar-phosphate unit of the strand. [App]
nucleus (pl. nuclei)
1. A collection of neuronal cell bodies within the central nervous system (e.g., the caudate nucleus). Compare ganglion. [2] 2. See cell nucleus. [App]
nucleus accumbens
A region of the forebrain that receives dopaminergic innervation from the ventral tegmental area, often associated with reward and pleasurable sensations. [4, 11]
nucleus of the solitary tract (NST)
A complicated brainstem nucleus that receives visceral and taste information via several cranial nerves. See Figure 9.15. [9]
nutrient
A chemical that is needed for growth, maintenance, and repair of the body but is not used as a source of energy. [9]

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O

obsessive-compulsive disorder (OCD)
An anxiety disorder in which the affected individual experiences recurrent unwanted thoughts and engages in repetitive behaviors without reason or the ability to stop. [12]
occipital cortex
Also called visual cortex. Cortex of the occipital lobe of the brain, corresponding to the primary visual area of the cortex. See Figure 7.10. [7]
occipital lobe
A large region of cortex that covers much of the posterior part of each cerebral hemisphere. See Figure 2.10. Compare frontal lobe, parietal lobe, and temporal lobe. [2]
OCD
See obsessive-compulsive disorder. [12]
ocular dominance histogram
A graph that plots how strongly a brain neuron responds to stimuli presented to either the left eye or the right eye. Ocular dominance histograms are used to determine the effects of manipulating visual experience. [ASF 13.4]
odor
The sensation of smell. [6]
off-center bipolar cell
A retinal bipolar cell that is inhibited by light in the center of its receptive field. See Figures 7.13, 7.14. Compare on-center bipolar cell. [7]
off-center ganglion cell
A retinal ganglion cell that is activated when light is presented to the periphery, rather than the center, of the cell’s receptive field. See Figures 7.13, 7.14. Compare on-center ganglion cell. [7]
off-center/on-surround
Referring to a concentric receptive field in which stimulation of the center inhibits the cell of interest while stimulation of the surround excites it. See Figure 7.14. Compare on-center/off-surround. [7]
OHC
See outer hair cell. [6]
olfaction
The sensory system that detects smell; the act of smelling. [6]
olfactory bulb
An anterior projection of the brain that terminates in the upper nasal passages and, through small openings in the skull, provides receptors for smell. See Figures 2.10, 2.16, 6.19. [2, 6]
olfactory epithelium (pl. epithelia)
A sheet of cells, including olfactory receptors, that lines the dorsal portion of the nasal cavities and adjacent regions. See Figures 6.18, 6.19. [6]
oligodendrocyte
A type of glial cell that forms myelin in the central nervous system. See Figure 2.5. Compare Schwann cell. [2]
on-center bipolar cell
A retinal bipolar cell that is excited by light in the center of its receptive field. See Figures 7.13 7.14. Compare off-center bipolar cell. [7]
on-center ganglion cell
A retinal ganglion cell that is activated when light is presented to the center, rather than the periphery, of the cell’s receptive field. See Figures 7.13, 7.14. Compare off-center ganglion cell. [7]
on-center/off-surround
Referring to a concentric receptive field in which stimulation of the center excites the cell of interest while stimulation of the surround inhibits it. See Figure 7.14. Compare off-center/on-surround. [7]
ontogeny
The process by which an individual changes in the course of its lifetime—that is, grows up and grows old. [1]
Onuf’s nucleus
The human homolog of the spinal nucleus of the bulbocavernosus (SNB) in rats. [8]
operant conditioning
See instrumental conditioning. [13]
opiate
Any of a class of compounds that exert an effect like that of opium, including reduced pain sensitivity. [4]
opioid peptide
A type of endogenous peptide that mimics the effects of morphine in binding to opioid receptors and producing marked analgesia and reward. See Table 4.1. [4]
opioid receptor
A receptor that responds to endogenous opioids and/or exogenous opiates. [4]
opium
An extract of the seedpod juice of the opium poppy, Papaver somniferum. Drugs based on opium are potent painkillers. [4]
opponent-process hypothesis
A hypothesis of color perception stating that different systems produce opposite responses to light of different wavelengths. See Figures 7.23, 7.24. [7]
optic ataxia
Spatial disorientation in which the patient is unable to accurately reach for objects using visual guidance. [7]
optic chiasm
The point at which parts of the two optic nerves cross the midline. See Figure 7.10. [7]
optic disc
The region of the retina that is devoid of receptor cells because ganglion cell axons and blood vessels exit the eyeball there. See Figure 7.7. [7]
optic nerve
Cranial nerve II; the collection of ganglion cell axons that extend from the retina to the brain. See Figures 2.7, 7.10. [7]
optic radiation
Axons from the lateral geniculate nucleus that terminate in the primary visual areas of the occipital cortex. See Figure 7.10. [7]
optic tract
The axons of retinal ganglion cells after they have passed the optic chiasm. Most of these axons terminate in the lateral geniculate nucleus. See Figure 7.10. [7]
optogenetics
The use of lasers to excite or inhibit neurons expressing light-sensitive membrane channels, typically in transgenic mice. [11]
oral contraceptive
A birth control pill, typically consisting of steroid hormones to prevent ovulation. [8]
orexin
Also called hypocretin. A neuropeptide produced in the hypothalamus that is involved in switching between sleep states, in narcolepsy, and in the control of appetite. [9, 10]
organ of Corti
A structure in the inner ear that lies on the basilar membrane of the cochlea and contains the hair cells and terminations of the auditory nerve. See Figure 6.1. [6]
organizational effect
A permanent alteration of the nervous system, and thus permanent change in behavior, resulting from the action of a steroid hormone on an animal early in its development. Compare activational effect. [8]
orgasm
The climax of sexual behavior, marked by extremely pleasurable sensations. [8]
osmosensory neuron
A specialized neuron that monitors the concentration of the extracellular fluid by measuring the movement of water into and out of the intracellular compartment. See Figures 9.7, 9.9. [9]
osmosis
The passive movement of a solvent, usually water, through a semipermeable membrane until a uniform concentration of solute (often salt) is achieved on both sides of the membrane. See Figure 9.6. Compare diffusion. [9]
osmotic pressure
The tendency of a solvent to move across a membrane in order to equalize the concentration of solute on both sides of the membrane. [9]
osmotic thirst
A desire to ingest fluids that is stimulated by a high concentration of solute (like salt) in the extracellular compartment. Compare hypovolemic thirst. [9]
ossicles
Three small bones (incus, malleus, and stapes) that transmit vibrations across the middle ear, from the tympanic membrane to the oval window. See Figure 6.1. [6]
otolith
A small crystal on the gelatinous membrane in the vestibular system.
outer hair cell (OHC)
One of the two types of receptor cells for hearing in the cochlea. Compared with inner hair cells, OHCs are positioned farther from the central axis of the coiled cochlea. See Figure 6.1. [6]
output zone
The part of a neuron at which the cell sends information to another cell. This zone usually corresponds to the axon terminals. See Figures 2.1, 2.3. Compare conduction zone, input zone, and integration zone. [2]
oval window
The opening from the middle ear to the inner ear. See Figure 6.1. [6]
ovaries
The female gonads, which produce eggs (ova) for reproduction. See Figure 8.1. Compare testes. [8]
overt attention
Attention in which the focus coincides with sensory orientation (e.g., you’re attending to the same thing you’re looking at). Compare covert attention. [14]
ovulation
The production and release of an egg (ovum). [8]
ovulatory cycle
The periodic occurrence of ovulation in females. See Figure 8.19. [8]
ovum (pl. ova)
An egg, the female gamete. Compare sperm. [8]
oxytocin
A hormone, released from the posterior pituitary, that triggers milk letdown in the nursing female but is also associated with a variety of complex behaviors. See Figures 8.8, 8.9. [8]

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P

P1 effect
See visual P1 effect. [14]
P3 effect
Also called auditory P300. A positive deflection of the event-related potential, occurring about 300 milliseconds after stimulus presentation, that is associated with higher-order auditory stimulus processing and late attentional selection. [14]
P20–50 effect
A positive deflection of the event-related potential, occurring about 20–50 milliseconds after stimulus presentation, that is enhanced for selectively attended auditory input compared with ignored input. [14]
Pacinian corpuscle
Also called lamellated corpuscle. A skin receptor cell type that detects vibration and pressure. See Figures 5.3, 5.4. Compare Meissner’s corpuscle, Merkel’s disc, and Ruffini corpuscle. [5]
pain
The discomfort normally associated with tissue damage. [5]
pair-bond
A durable and exclusive relationship between two individuals. [8]
Papez circuit
A group of brain regions within the limbic system.
papilla (pl. papillae)
A small bump that projects from the surface of the tongue. Papillae contain most of the taste receptor cells. See Figures 6.15, 6.16. [6]
parabiotic
Referring to a surgical preparation that joins two animals to share a single blood supply. [8]
paradoxical sleep
See rapid-eye-movement sleep (REM) sleep. [10]
paraphasia
A symptom of aphasia that is distinguished by the substitution of a word by a sound, an incorrect word, an unintended word, or a neologism (a meaningless word). [15]
parasympathetic nervous system
The part of the autonomic nervous system that generally prepares the body to relax and recuperate. See Figure 2.9. Compare sympathetic nervous system. [2, 11]
parental behavior
Behavior of adult animals that has the goal of enhancing the well-being of their own offspring, often at some cost to the parents. [8]
paresis
Muscular weakness, often the result of damage to motor cortex. Compare plegia. [5]
parietal lobe
The large region of cortex lying between the frontal and occipital lobes in each cerebral hemisphere. See Figure 2.10. Compare also temporal lobe. [2]
parkin
A protein that has been implicated in Parkinson’s disease. [ASF 5.5]
Parkinson’s disease
A degenerative neurological disorder, characterized by tremors at rest, muscular rigidity, and reduction in voluntary movement, caused by loss of the dopaminergic neurons of the substantia nigra. Compare Huntington’s disease. [5]
partial agonist
A drug that, when bound to a receptor, has less effect than the endogenous ligand would. The term partial antagonist is equivalent. [4]
patient H.M.
The late Henry Molaison, a patient who was unable to encode new declarative memories because of surgical removal of medial temporal lobe structures.. See Figure 13.1. [13]
patient K.C.
The late Kent Cochrane, a patient who sustained damage to cortex that rendered him unable to form and retrieve episodic memories. [13]
patient N.A.
A still-living patient who is unable to encode new declarative memories, because of damage to the dorsomedial thalamus and the mammillary bodies. [13]
Pavlovian conditioning
See classical conditioning. [13]
PCP
See phencyclidine. [12]
PCR
See polymerase chain reaction. [App]
penis
The male phallus. Compare clitoris. [8]
peptide
A short string of amino acids. Longer strings of amino acids are called proteins. [App]
peptide hormone
Also called protein hormone. A hormone that consists of a string of amino acids. [8]
peptide neurotransmitter
Also called neuropeptide. A neurotransmitter consisting of a short chain of amino acids. See Table 4.1. Compare amine neurotransmitter, amino acid neurotransmitter, and gas neurotransmitter. [4]
perceptual load
The immediate processing demands presented by a stimulus. [14]
periaqueductal gray
A midbrain region involved in pain perception. [2, 4, 8]
period
The interval of time between two similar points of successive cycles, such as sunset to sunset. [10]
peripheral nervous system
The portion of the nervous system that includes all the nerves and neurons outside the brain and spinal cord. See Figures 2.6, 2.12. Compare central nervous system. [2]
peripheral spatial cuing
A technique for testing exogenous attention in which a visual stimulus is preceded by a simple task-irrelevant sensory stimulus either in the location where the stimulus will appear or in an incorrect location. Compare symbolic cuing. [14]
perseverate
To continue to show a behavior repeatedly. [14, ASF 13.4]
PET
See positron emission tomography. [2]
petit mal seizure
Also called absence attack. A seizure that is characterized by a spike-and-wave EEG and often involves a loss of awareness and inability to recall events surrounding the seizure. See Figure 3.16. Compare grand mal seizure. [3]
phagocyte
An immune system cell that engulfs invading molecules or microbes. [ASF 11.4]
phallus
The clitoris or penis. [8]
pharmacokinetics
Collective name for all the factors that affect the movement of a drug into, through, and out of the body. [4]
phase shift
A shift in the activity of a biological rhythm, typically provided by a synchronizing environmental stimulus. [10]
phasic receptor
A receptor in which the frequency of action potentials drops rapidly as stimulation is maintained. Compare tonic receptor. [5]
phencyclidine (PCP)
Also called angel dust. An anesthetic agent that is also a psychedelic drug. PCP makes many people feel dissociated from themselves and their environment. [12]
phenotype
The sum of an individual’s physical characteristics at one particular time. Compare genotype. [13]
phenylketonuria (PKU)
An inherited disorder of protein metabolism in which the absence of an enzyme leads to a toxic buildup of certain compounds, causing intellectual disability. [13]
pheromone
A chemical signal that is released outside the body of an animal and affects other members of the same species. See Figure 8.3. Compare allomone. [6, 8]
phoneme
A sound that is produced for language. [15]
photopic system
A system in the retina that operates at high levels of light, shows sensitivity to color, and involves the cones. See Table 7.1. Compare scotopic system. [7]
photoreceptor
A neural cell in the retina that responds to light. [7]
photoreceptor adaptation
The tendency of rods and cones to adjust their light sensitivity to match current levels of illumination. [7]
phrenology
The belief that bumps on the skull reflect enlargements of brain regions responsible for certain behavioral faculties. See Figure 1.4. [1]
physiological psychology
See biological psychology. [1]
pia mater
The innermost of the three meninges that surround the brain and spinal cord. See also dura mater and arachnoid. See Figure 2.8. [2]
pineal gland
A secretory gland in the brain midline that is the source of melatonin release. See Figure 8.1. [8, ASF 8.1]
pinna (pl. pinnae)
The external part of the ear. [6]
pitch
A dimension of auditory experience in which sounds vary from low to high. See Box 6.1. [6]
pituitary gland
A small, complex endocrine gland located in a socket at the base of the skull. See Figures 2.16, 8.8, 8.12. [8]
pituitary stalk
Also called infundibulum. A thin piece of tissue that connects the pituitary gland to the hypothalamus. [8]
PKU
See phenylketonuria. [13]
place cell
A neuron in the hippocampus that selectively fires when the animal is in a particular location. [13]
place coding
Frequency discrimination in which the pitch of a sound is determined by the location of activated hair cells along the length of the basilar membrane. Compare temporal coding. [6]
placebo effect
Relief of a symptom, such as pain, that results following a treatment that is known to be ineffective or inert. [5]
planum temporale
An auditory region of superior temporal cortex. See Figure 15.3. [15]
plegia
Paralysis, the loss of the ability to move. Compare paresis. [5]
polarized
Exhibiting a difference in electrical charge between the inside and outside of the cell. [3]
poliovirus
A virus that destroys motoneurons of the spinal cord and brainstem, causing permanent paralysis. [ASF 5.5]
polygraph
Popularly known as a lie detector. A device that measures several bodily responses, such as heart rate and blood pressure. See Box 11.1. [11]
polymerase chain reaction (PCR)
Also called gene amplification. A method for reproducing a particular RNA or DNA sequence manyfold, allowing amplification for sequencing or manipulating the sequence. [App]
polymodal
Also called multisensory. Involving several sensory modalities. [ASF 6.3]
polymodal neuron
A neuron upon which information from more than one sensory system converges. [5]
POMC neuron
A neuron, involved in the hypothalamic appetite control system, that produces both pro-opiomelanocortin and cocaine- and amphetamine-related transcript. Compare NPY neuron. [9]
pons
The portion of the brainstem that connects the midbrain to the medulla. See Figures 2.12, 2.16. [2]
positive correlation
A covariation of two measures in which they both usually increase together, or decrease together. Compare negative correlation. [1]
positive symptom
In psychiatry, an abnormal behavioral state. Examples include hallucinations, delusions, and excited motor behavior. Compare negative symptom. [12]
positron emission tomography (PET)
A brain imaging technology that tracks the metabolism of injected radioactive substances in the brain, in order to map brain activity.. See Figure 2.19. Compare functional MRI. [2]
postcentral gyrus
The strip of parietal cortex, just behind the central sulcus, that receives somatosensory information from the entire body. See Figure 2.10. Compare precentral gyrus. [2]
postcopulatory behavior
The final stage in mating behavior. Species-specific postcopulatory behaviors include rolling (in the cat) and grooming (in the rat). See Figure 8.16. [8]
posterior
Also called caudal. In anatomy, toward the tail end of an organism. See Box 2.2. Compare anterior. [2]
posterior cerebral artery
Either of two large arteries, arising from the basilar artery, that provide blood to posterior aspects of the cerebral hemispheres, cerebellum, and brainstem. Compare anterior cerebral artery and middle cerebral artery. [ASF 2.1]
posterior pituitary
The rear division of the pituitary gland. See Figures 8.1, 8.8. Compare anterior pituitary. [8]
postpartum depression
A bout of depression that afflicts a woman either immediately before or after giving birth. [12]
postsynaptic
Referring to the region of a synapse that receives and responds to neurotransmitter. See Figure 2.4. Compare presynaptic. [2, 3, 4]
postsynaptic membrane
The specialized membrane on the surface of a neuron that receives information by responding to neurotransmitter from a presynaptic neuron. See Figure 2.4. Compare presynaptic membrane. [2]
postsynaptic potential
A local potential that is initiated by stimulation at a synapse, which can vary in amplitude, and spreads passively across the cell membrane, decreasing in strength with time and distance. Compare all-or-none property. [3]
posttraumatic stress disorder (PTSD)
A disorder in which memories of an unpleasant episode repeatedly plague the victim. See Box 13.1. [12, 13]
potassium ion (K+)
A potassium atom that carries a positive charge. [3]
precentral gyrus
The strip of frontal cortex, just in front of the central sulcus, that is crucial for motor control. See Figure 2.10. Compare postcentral gyrus. [2, 5]
prefrontal cortex
The anteriormost region of the frontal lobe. [14]
premotor cortex
A region of nonprimary motor cortex just anterior to the primary motor cortex. See Figure 5.25. [5]
presenilin
An enzyme that cleaves amyloid precursor protein, forming beta-amyloid, which can lead to Alzheimer’s disease. See beta-secretase. [ASF 13.5]
presynaptic
Located on the “transmitting” side of a synapse. See Figure 2.4. Compare postsynaptic. [2, 3, 4]
presynaptic membrane
The specialized membrane on the axon terminal of a nerve cell that transmits information by releasing neurotransmitter. See Figure 2.4. [2]
primacy effect
The superior performance seen in a memory task for items at the start of a list. It is usually attributed to long-term memory. See Figure 13.14. Compare recency effect. [13]
primary auditory cortex
Also called A1. The cortical region, located on the superior surface of the temporal lobe, that processes complex sounds transmitted from lower auditory pathways. [6]
primary motor cortex (M1)
The apparent executive region for the initiation of movement. It is primarily the precentral gyrus. Compare nonprimary motor cortex. [5]
primary sensory cortex
For a given sensory modality, the region of cortex that receives most of the information about that modality from the thalamus (or, in the case of olfaction, directly from the secondary sensory neurons). Compare nonprimary sensory cortex. [5]
primary somatosensory cortex
Also called somatosensory 1 or S1. Primarily the post-central gyrus of the parietal lobe, , where sensory inputs from the body surface are mapped. See Figures 5.7, 5.9. [5]
primary visual cortex (V1)
Also called striate cortex or area 17. The region of the occipital cortex where most visual information first arrives. See Figures 7.10, 7.11, 7.20. [7]
priming
Also called repetition priming. In memory, the phenomenon by which exposure to a stimulus facilitates subsequent responses to the same or a similar stimulus. [13]
probe
In molecular biology, a manufactured sequence of DNA that is made to include a label (a colorful or radioactive molecule) that lets us track its location. [App]
procedural memory
See nondeclarative memory. [13]
proceptive
Referring to a state in which a female advertises its readiness to mate through species-typical behaviors. [8]
progesterone
The primary type of progestin secreted by the ovary. See Figure 8.13. [8]
progestin
Any of a major class of steroid hormones that are produced by the ovary, including progesterone. See Figure 8.13. [8]
progressive supranuclear palsy (PSP)
A rare, degenerative disease of the brain that begins with marked, persistent visual symptoms and leads to more widespread intellectual deterioration. [14]
prolactin
A protein hormone, produced by the anterior pituitary, that promotes mammary development for lactation in female mammals. [ASF 8.3]
proprioception
Body sense; information about the position and movement of the body. [5]
prosody
The perception of emotional tone-of-voice aspects of language. [15]
prosopagnosia
Also called face blindness. A condition characterized by the inability to recognize faces. [15]
protein
A long string of amino acids. Proteins are the basic building material of organisms. Compare peptide. [App]
protein hormone
See peptide hormone.
proximal
In anatomy, near the trunk or center of an organism. See Box 2.2. Compare distal. [2]
PSP
See progressive supranuclear palsy. [14]
psychoneuroimmunology
The study of the immune system and its interaction with the nervous system and behavior. [11]
psychopath
An individual incapable of experiencing remorse. [11]
psychosocial dwarfism
A syndrome of stunted growth in children subjected to social stress, such as abusive caregivers. See Figure 8.36. [8]
psychosomatic medicine
A field of study that emphasizes the role of psychological factors in disease. [11]
psychosurgery
Surgery in which brain lesions are produced to modify severe psychiatric disorders.
psychotomimetic
A drug that induces a state resembling schizophrenia. [12]
PTSD
See posttraumatic stress disorder. [12, 13]
pulvinar
In humans, the posterior portion of the thalamus. It is heavily involved in visual processing and direction of attention. [14]
punch-drunk syndrome
See chronic traumatic encephalopathy. [15]
pupil
The opening, formed by the iris, that allows light to enter the eye. See Figures 7.1, 7.6. [7]
pure tone
A tone with a single frequency of vibration. See Box 6.1. [6]
Purkinje cell
A type of large nerve cell in the cerebellar cortex.
putamen
One of the basal ganglia. See Figure 2.14. [2]
pyramidal cell
A type of large nerve cell that has a roughly pyramid-shaped cell body and is found in the cerebral cortex. See Figure 2.13. [2]
pyramidal system
Also called corticospinal system. The motor system that includes neurons within the cerebral cortex and their axons, which form the pyramidal tract. See Figure 5.22. Compare extrapyramidal system. [5]
PYY3-36
A peptide hormone, secreted by the intestines, that probably acts on hypothalamic appetite control mechanisms to suppress appetite. Compare ghrelin. [9]

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Q

quale (pl. qualia)
A purely subjective experience of perception. [14]

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R

range fractionation
The means by which sensory systems cover a wide range of intensity values, as each sensory receptor cell specializes in just one part of the overall range of intensities. [7]
raphe nuclei
A string of nuclei in the midline of the midbrain and brainstem that contain most of the serotonergic neurons of the brain. [4]
rapid-eye-movement (REM) sleep
Also called paradoxical sleep. A stage of sleep characterized by small-amplitude, fast-EEG waves, flaccid muscles, and rapid eye movements. REM rhymes with “gem.” See Figure 10.9. Compare stage 3 sleep. [10]
RBD
See REM behavior disorder. [10]
recency effect
The superior performance seen in a memory task for items at the end of a list. It is usually attributed to short-term memory. See Figure 13.14. Compare primacy effect. [13]
receptive field
The stimulus region and features that affect the activity of a cell in a sensory system. See Figures 5.5, 7.14, 7.17. [5, 7]
receptor
See neurotransmitter receptor. [2, 3, 4]
receptor cell
A specialized cell that responds to a particular energy or substance in the internal or external environment and converts this energy into a change in the electrical potential across its membrane. [5]
receptor subtype
Any type of receptor having functional characteristics that distinguish it from other types of receptors for the same neurotransmitter. For example, at least 15 different subtypes of receptor molecules respond to serotonin.
reconsolidation
The return of a memory trace to stable long-term storage after it has been temporarily made changeable during the process of recall. [13]
recovery of function
The recovery of behavioral capacity following brain damage from stroke or injury. [15]
reductionism
The scientific strategy of breaking a system down into increasingly smaller parts in order to understand it. [1]
reflex
A simple, highly stereotyped, and unlearned response to a particular stimulus (e.g., an eye blink in response to a puff of air). See Figures 3.14, 5.21. [5]
reflexive attention
See exogenous attention. [14]
refraction
The bending of light rays by a change in the density of a medium, such as the cornea and the lens of the eyes. [7]
refractory
Temporarily unresponsive or inactivated. [3]
refractory phase
1. A period during and after an action potential in which the responsiveness of the axonal membrane is reduced. A brief period of complete insensitivity to stimuli (absolute refractory phase) is followed by a longer period of reduced sensitivity (relative refractory phase) during which only strong stimulation produces an action potential. [3] 2. A period following copulation during which an individual does not recommence copulation. See Figure 8.23. [8]
relative refractory phase
A period of reduced sensitivity during which only strong stimulation produces an action potential. Compare absolute refractory phase. [3]
releasing hormone
Any of a class of hormones, produced in the hypothalamus, that traverse the hypothalamic-pituitary portal system to control the pituitary’s release of tropic hormones. See Figure 8.12. [8]
REM behavior disorder (RBD)
A sleep disorder in which a person physically acts out a dream. [10]
REM sleep
See rapid-eye-movement (REM) sleep. [10]
repetition priming
See priming. [13]
repetitive transcranial magnetic stimulation (rTMS)
A noninvasive treatment in which repeated pulses of focused magnetic energy are used to stimulate the cortex through the scalp. [12]
resting potential
The difference in electrical potential across the membrane of a nerve cell at rest. See Figures 3.1, 3.5. [3]
reticular formation
Also called reticular activating system. An extensive region of the brainstem (extending from the medulla through the thalamus) that is involved in arousal (waking). See Figure 10.18. [2, 10]
retina
The receptive surface inside the eye that contains photoreceptors and other neurons. See Figures 7.1, 7.3. [7]
retinohypothalamic pathway
The route by which retinal ganglion cells send their axons to the suprachiasmatic nuclei. [10]
retrieval
The third process of the memory system, in which a stored memory is used by an organism. See Figure 13.13. Compare encoding and consolidation. [13]
retrograde amnesia
Difficulty in retrieving memories formed before the onset of amnesia. Compare anterograde amnesia. [13]
retrograde transmitter
A neurotransmitter that is released by the postsynaptic region, diffuses back across the synapse, and alters the functioning of the presynaptic neuron. [4, 13]
reuptake
The process by which released synaptic transmitter molecules are taken up and reused by the presynaptic neuron, thus stopping synaptic activity. [3, 4]
rhodopsin
The photopigment in rods that responds to light. [7]
ribonucleic acid (RNA)
A nucleic acid that implements information found in DNA. Compare deoxyribonucleic acid. [App]
ribosome
An organelle in the cell body where genetic information is translated to produce proteins. See Appendix Figure A.2. [App]
RNA
See ribonucleic acid (RNA). [App]
rod
A photoreceptor cell in the retina that is most active at low levels of light. See Figure 7.3. Compare cone. [7]
root
Either of two distinct branches of a spinal nerve, each of which serves a separate function. The dorsal root enters the dorsal horn of the spinal cord and carries sensory information, the ventral root arises from the ventral horn of the spinal cord and carries motor messages. See Figure 2.8. [2]
rostral
See anterior. [2]
round window
A membrane separating the tympanic canal from the middle ear. See Figure 6.1. [6]
Ruffini corpuscle
A skin receptor cell type that detects stretching of the skin. See Figure 5.3. Compare Meissner’s corpuscle, Merkel’s disc, and Pacinian corpuscle. [5]

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S

S1
See primary somatosensory cortex. [5]
sacral
Referring to the five spinal segments that make up the lower part of the lower back. See Figures 2.8, 2.9. Compare cervical, thoracic, lumbar, and coccygeal. [2]
SAD
See seasonal affective disorder. [ASF 12.3]
sagittal plane
The plane that divides the body or brain into right and left portions. See Box 2.2. Compare coronal plane and horizontal plane. [2]
saltatory conduction
The form of conduction that is characteristic of myelinated axons, in which the action potential jumps from one node of Ranvier to the next. [3]
satiety
A feeling of fulfillment or satisfaction. Compare hunger. [9]
saturation
One of three basic dimensions of light perception, varying from rich to pale. Compare brightness and hue. [7]
SC
See standard condition. [13]
scala media
Also called middle canal. The central of the three spiraling canals inside the cochlea, situated between the scala vestibuli and the scala tympani. See Figure 6.1. [6]
scala tympani
Also called tympanic canal. One of three principal canals running along the length of the cochlea. Compare scala media and scala vestibuli. See Figure 6.1. [6]
scala vestibuli
Also called vestibular canal. One of three principal canals running along the length of the cochlea. Compare scala media and scala tympani. See Figure 6.1. [6]
schizophrenia
A severe psychopathological disorder characterized by negative symptoms such as emotional withdrawal and flat affect and by positive symptoms such as hallucinations and delusions. [12]
Schwann cell
A type of glial cell that forms myelin in the peripheral nervous system. Compare oligodendrocyte. [2]
SCN
See suprachiasmatic nucleus. [10]
scotoma
A region of blindness within the visual fields, caused by injury to the visual pathway or brain. [7]
scotopic system
A system in the retina that operates at low levels of light and involves the rods. See Table 7.1. Compare photopic system. [7]
SDN-POA
See sexually dimorphic nucleus of the preoptic area. [8]
seasonal affective disorder (SAD)
A depression putatively brought about by the short days of winter. [ASF 12.3]
second messenger
A slow-acting substance in a target cell that amplifies the effects of synaptic or hormonal activity and regulates activity within the target cell. [8]
secondary sensory cortex
See nonprimary sensory cortex. [5]
seizure
A wave of abnormally synchronous electrical activity in the brain. See Figure 3.16. [3]
selective attention
See attention. [14]
selective permeability
The property of a membrane that allows some substances to pass through, but not others. [3]
selective serotonin reuptake inhibitor (SSRI)
An antidepressant drug that blocks the reuptake of transmitter at serotonergic synapses. [4, 12]
semantic memory
Generalized declarative memory, such as knowing the meaning of a word. Compare episodic memory. [13]
semantics
The meanings or interpretation of words and sentences in a language.
semen
A mixture of fluid and sperm that is released during ejaculation. [8]
semicircular canal
Any one of the three fluid-filled tubes in the inner ear that are part of the vestibular system. Each of the tubes, which are at right angles to each other, detects angular acceleration in a particular direction. See Figure 6.14. [6]
senile dementia
A neurological disorder of the aged that is characterized by progressive behavioral deterioration, including personality change and profound intellectual decline. It includes, but is not limited to, Alzheimer’s disease.
senile plaque
See amyloid plaque. [13]
sensitive period
Also called critical period. The period during development in which an organism can be permanently altered by a particular experience or treatment. [8, 15, ASF 13.4]
sensorineural deafness
A hearing impairment most often caused by the permanent damage or destruction of hair cells, or by interruption of the vestibulocochlear nerve that carries auditory information to the brain. See Figure 6.11. Compare central deafness and conduction deafness. [6]
sensory adaptation
The progressive loss of receptor response as stimulation is maintained. See Figure 5.6. [5]
sensory buffer
A very brief type of memory that stores the sensory impression of a scene. In vision, it is sometimes called iconic memory. See Figure 13.13. [13]
sensory nerve
A nerve that conveys information from the body to the central nervous system. Compare motor nerve. [2]
sensory neuron
A nerve cell that is directly affected by changes in the environment, such as light, odor, or touch. Compare interneuron and motoneuron. [2]
sensory transduction
The process in which a receptor cell converts the energy in a stimulus into a change in the electrical potential across its membrane. [5]
serotonergic
Referring to cells that use serotonin as their synaptic transmitter. [4]
serotonin (5-HT)
A synaptic transmitter that is produced in the raphe nuclei and is active in structures throughout the central nervous system. See Figure 4.4; Table 4.1. [4, 11]
set point
The point of reference in a feedback system. An example is the temperature at which a thermostat is set. Compare set zone. [9]
set zone
The optimal range of a variable that a feedback system tries to maintain. Compare set point. [9]
sex determination
The process that normally establishes whether a fetus will develop as a male or a female. [8]
sexual attraction
The first step in the mating behavior of many animals, in which animals emit stimuli that attract members of the opposite sex. See Figure 8.16. [8]
sexual differentiation
The process by which individuals develop either malelike or femalelike bodies and behavior. See Figure 8.24. [8]
sexual dimorphism
The condition in which males and females of the same species show pronounced sex differences in appearance. [8]
sexually dimorphic nucleus of the preoptic area (SDN-POA)
A region of the preoptic area that is 5 to 6 times larger in volume in male than in females rats. See Figure 8.30. [8]
sexually receptive
Referring to the state in which an individual (in mammals, typically the female) is willing to copulate. [8]
shadowing
A task in which the subject is asked to focus attention on one ear or the other while stimuli are being presented separately to both ears, and to repeat aloud the material presented to the attended ear. [14]
sham rage
See decorticate rage. [11]
shivering
Rapid involuntary muscle contractions that generate heat in hypothermic animals. [ASF 9.1]
short-term memory (STM)
Also called working memory. A form of memory that usually lasts only seconds, or as long as rehearsal continues. See Figure 13.13. Compare sensory buffer and long-term memory. [13]
SIDS
See sudden infant death syndrome. [10]
simple cortical cell
Also called bar detector or edge detector. A cell in the visual cortex that responds best to an edge or a bar that has a particular width, as well as a particular orientation and location in the visual field. Compare complex cortical cell. [7]
simultagnosia
A profound restriction of attention, often limited to a single item or feature. Simultagnosia is one of the three primary symptoms of Balint’s syndrome. [14]
skeletal muscle
A muscle that is used for movement of the skeleton, typically under our conscious control. [5]
skill learning
The process of learning to perform a challenging task simply by repeating it over and over. [13]
sleep apnea
A sleep disorder in which respiration slows or stops periodically, waking the patient. Excessive daytime sleepiness results from the frequent nocturnal awakening. [10]
sleep cycle
A period of slow-wave sleep followed by a period of REM sleep. In humans, a sleep cycle lasts 90–110 minutes.
sleep deprivation
The partial or total prevention of sleep. [10]
sleep enuresis
Bed-wetting. [10]
sleep-maintenance insomnia
Difficulty in staying asleep. Compare sleep-onset insomnia. [10]
sleep-onset insomnia
Difficulty in falling sleep. Compare sleep-maintenance insomnia. [10]
sleep paralysis
A state, during the transition to or from sleep, in which the ability to move or talk is temporarily lost. [10]
sleep recovery
The process of sleeping more than normally after a period of sleep deprivation, as though in compensation. [10]
sleep spindle
A characteristic 14- to 18-hertz wave in the EEG of a person said to be in stage 2 sleep. See Figure 10.9. [10]
sleep state misperception
Commonly, a person’s perception that he has not been asleep when in fact he has. It typically occurs at the start of a sleep episode. [10]
slow wave sleep (SWS)
Also called non-REM sleep. Sleep, divided into stages 1–3, that is defined by the presence of slow-wave EEG activity. See Figure 10.9. Compare rapid-eye-movement (REM) sleep. [10]
SMA
See supplementary motor area. [5]
SNB
See spinal nucleus of the bulbocavernosus. [8]
social neuroscience
A field of study that uses the tools of neuroscience to discover both the biological bases of social behavior and the effects of social circumstances on brain activity. [1]
sodium ion (Na+)
A sodium atom that carries a positive charge. [3]
sodium-potassium pump
The energetically expensive mechanism that pushes sodium ions out of a cell, and potassium ions in. [3]
solute
A solid compound that is dissolved in a liquid. Compare solvent.
solvent
The liquid (often water) in which a compound is dissolved. Compare solute.
soma (pl. somata)
See cell body. [2]
somatic intervention
An approach to finding relations between body variables and behavioral variables that involves manipulating body structure or function and looking for resultant changes in behavior. See Figure 1.9. Compare behavioral intervention. [1]
somatic nerve
See spinal nerve. [2]
somatic nervous system
A part of the peripheral nervous system that supplies neural connections mostly to the skeletal muscles and sensory systems of the body. It consists of cranial nerves and spinal nerves. [2]
somatosensory 1 (S1)
See primary somatosensory cortex. [5]
somatosensory system
A set of specialized receptors and neural mechanisms responsible for body sensations such as touch and pain. [5]
somatotropic hormone
Also called somatotropin. See growth hormone. [8]
somnambulism
Sleepwalking. [10]
Southern blot
A method of detecting a particular DNA sequence in the genome of an organism by separating DNA with gel electrophoresis, blotting the separated DNA molecules onto nitrocellulose, and then using a nucleotide probe to hybridize with, and highlight, the gene of interest. See Appendix Figure A.3. Compare Northern blot and Western blot. [App]
spasticity
Markedly increased rigidity in response to forced movement of the limbs.
spatial cognition
The ability to navigate and to understand the spatial relationship between objects. [15]
spatial-frequency model
A model of vision that emphasizes the analysis of different spatial frequencies, of various orientations and in various parts of the visual field, as the basis of visual perception of form. [7, ASF 7.2]
spatial resolution
The ability to observe the detailed structure of the brain. Compare temporal resolution. [14]
spatial summation
The summation of postsynaptic potentials that reach the axon hillock from different locations across the cell body. If this summation reaches threshold, an action potential is triggered. See Figure 3.10. Compare temporal summation. [3]
spectral filtering
The process by which the hills and valleys of the external ear alter the amplitude of some, but not all, frequencies in a sound. [6]
spectrally opponent cell
Also called color-opponent cell. A visual receptor neuron that has opposite firing responses to different regions of the spectrum. See Figures 7.26, 7.27. [7]
sperm
The gamete produced by males for the fertilization of eggs (ova). [8]
spike
See action potential. [3]
spinal nerve
Also called somatic nerve. A nerve that emerges from the spinal cord. There are 31 pairs of spinal nerves. Compare cranial nerve. See Figure 2.8. [2]
spinal nucleus of the bulbocavernosus (SNB)
A group of motoneurons in the spinal cord of rats that innervate muscles controlling the penis. See Figure 8.32. See also Onuf’s nucleus. [8]
spinocerebellum
The uppermost part of the cerebellum, consisting mostly of the vermis and the anterior lobe. It receives sensory information about the current spatial location of the parts of the body and anticipates subsequent movement. Compare cerebrocerebellum and vestibulocerebellum. [ASF 5.4]
spinothalamic system
See anterolateral system. [5]
split-brain individual
An individual whose corpus callosum has been severed, halting communication between the right and left hemispheres. [15]
SRY gene
A gene on the Y chromosome that directs the developing gonads to become testes. The name SRY stands for sex-determining region on the Y chromosome. [8]
SSRI
See selective serotonin reuptake inhibitor. [4, 12]
stage 1 sleep
The initial stage of non-REM sleep, which is characterized by small-amplitude EEG waves of irregular frequency, slow heart rate, and reduced muscle tension. See Figure 10.9. [10]
stage 2 sleep
A stage of sleep that is defined by bursts of regular 14- to 18-hertz EEG waves called sleep spindles. See Figure 10.9. [10]
stage 3 sleep
Also called slow wave sleep (SWS). A stage of non-REM sleep that is defined by the presence of large-amplitude, slow delta waves. See Figure 10.9. [10]
standard condition (SC)
The usual environment for laboratory rodents, with a few animals in a cage and adequate food and water, but no complex stimulation. See Figure 13.16. Compare enriched condition and impoverished condition. [13]
stapedius
A middle-ear muscle that is attached to the stapes. See Figure 6.1.
stapes
Latin for “stirrup.” A middle-ear bone that is connected to the oval window. It is one of the three ossicles that conduct sounds across the middle ear. See Figure 6.1. [6]
stem cell
A cell that is undifferentiated and therefore can take on the fate of any cell that a donor organism can produce. [13]
stereocilium (pl. stereocilia)
A tiny bristle that protrudes from a hair cell in the auditory or vestibular system. See Figure 6.1. [6]
steroid hormone
Any of a class of hormones, each of which is composed of four interconnected rings of carbon atoms. Compare amine hormone and peptide hormone. [8]
stimulant
A drug that enhances the excitability of neurons. Compare depressant. [4]
stimulus (pl. stimuli)
A physical event that triggers a sensory response. [5]
stimulus cuing
A technique for testing reaction time to sensory stimuli, in which a cue to where the stimulus will be presented is provided before the stimulus itself.
STM
See short-term memory. [13]
stress
Any circumstance that upsets homeostatic balance. [11]
stress immunization
The concept that mild stress early in life makes an individual better able to handle stress later in life. The benefits seem to be due to effective comforting after stressful events, not the stressful events themselves. [11]
stretch reflex
The contraction of a muscle in response to stretch of that muscle. See Figure 5.21. [5]
striate cortex
See primary visual cortex. [7]
striate muscle
A type of muscle that has a striped appearance. It is generally under voluntary control.[5]
striatum
The caudate nucleus and putamen together.
stroke
Damage to a region of brain tissue that results from the blockage or rupture of vessels that supply blood to that region. [2]
stuttering
The tendency of otherwise healthy people to produce speech sounds only haltingly, tripping over certain syllables or being unable to start vocalizing certain words. [15]
substance P
A peptide transmitter that is involved in pain transmission. [5]
substantia nigra
A brainstem structure that innervates the basal ganglia and is a major source of dopaminergic projections. Compare locus coeruleus. [2, 4, 5]
sudden infant death syndrome (SIDS)
Also called crib death. The sudden, unexpected death of an apparently healthy human infant who simply stops breathing, usually during sleep. [10]
sulcus (pl. sulci)
A crevice or valley of a convoluted brain surface. Compare gyrus. [2]
superior
In anatomy, above. See Box 2.2. Compare inferior. [2]
superior colliculi (sing. superior colliculus)
Paired gray matter structures of the dorsal midbrain that process visual information and are involved in direction of visual gaze and visual attention to intended stimuli. See Figures 2.16, 7.10. Compare inferior colliculi. [2, 7, 14]
superior olivary nucleus
Either of two brainstem nuclei—left and right—that receive input from both right and left cochlear nuclei, and provide the first binaural analysis of auditory information. See Figure 6.6. [6]
supersensitivity psychosis
An exaggerated psychosis that may emerge when doses of antipsychotic medication are reduced, probably as a consequence of the up-regulation of receptors that occurred during drug treatment. See Box 12.1. [12]
supplementary motor area (SMA)
A region of nonprimary motor cortex that receives input from the basal ganglia and modulates the activity of the primary motor cortex. See Figure 5.25. [5]
suprachiasmatic nucleus (SCN)
A small region of the hypothalamus above the optic chiasm that is the location of a circadian clock. [10]
surface dyslexia
Acquired dyslexia in which the patient seems to attend only to the fine details of reading. Compare deep dyslexia. [15]
sustained-attention task
A task in which a single stimulus source or location must be held in the attentional spotlight for a protracted period. Compare divided-attention task. [14]
SWS
See stage 3 sleep. [10]
Sylvian fissure
Also called lateral sulcus. A deep fissure that demarcates the temporal lobe. See Figure 2.10. [2]
symbolic cuing
A technique for testing endogenous attention in which a visual stimulus is presented and subjects are asked to respond as soon as the stimulus appears on a screen. Each trial is preceded by a meaningful symbol used as a cue to hint at where the stimulus will appear. Compare peripheral spatial cuing. [14]
sympathetic nervous system
The part of the autonomic nervous system that acts as the “fight or flight” system, generally activating the body for action. See Figure 2.9. Compare parasympathetic nervous system. [2, 11]
synapse
The cellular location at which information is transmitted from a neuron to another cell. See Figure 2.4. [2, 4, 8]
synapse rearrangement
Also called synaptic remodeling. The loss of some synapses and the development of others; a refinement of synaptic connections that is often seen in development. See Figure 13.25. [13]
synaptic bouton
See axon terminal. [2]
synaptic cleft
The space between the presynaptic and postsynaptic neurons at a synapse. This gap measures about 20–40 nm. See Figures 2.2, 2.4, 3.11. [2, 3]
synaptic delay
The brief delay between the arrival of an action potential at the axon terminal and the creation of a postsynaptic potential. [3]
synaptic remodeling
See synapse rearrangement. [13]
synaptic transmitter
See neurotransmitter. [2, 3]
synaptic vesicle
A small, spherical structure that contains molecules of neurotransmitter. See Figure 2.4. [2, 3]
synaptogenesis
The establishment of synaptic connections as axons and dendrites grow. See Figure 13.25. [13]
synergist
A muscle that acts together with another muscle. Compare antagonist (definition 2). [5]
synesthesia
A condition in which stimuli in one modality evoke the involuntary experience of an additional sensation in another modality. [5]
syrinx
The vocal organ in birds. [ASF 15.3]

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T

T cell
See T lymphocyte. [ASF 11.4]
T lymphocyte
Also called T cell. An immune system cell, formed in the thymus (hence the T), that attacks foreign microbes or tissue; “killer cell.” Compare B lymphocyte. [ASF 11.4]
T1R
A family of taste receptor proteins that, when particular members bind together, form taste receptors for sweet flavors and umami flavors. Compare T2R. [6]
T2R
A family of bitter taste receptors. Compare T1R. [6]
TAAR
See trace amine–associated receptor. [6]
tachistoscope test
A test in which stimuli are very briefly presented to either the left or right visual half field. [15]
tactile
Referring to touch.
tactile corpuscle
See Meissner’s corpuscle. [5]
tailbone
See coccygeal. [2]
tardive dyskinesia
A disorder characterized by involuntary movements, especially involving the face, mouth, lips, and tongue. It is related to prolonged use of antipsychotic drugs, such as chlorpromazine. See Box 12.1. [12]
taste
Any of the five basic sensations detected by the tongue: sweet, salty, sour, bitter, and umami. Compare flavor. [6]
taste bud
A cluster of 50–150 cells that detects tastes. Taste buds are found in papillae. See Figures 6.15, 6.16. [6]
tau
A protein associated with neurofibrillary tangles in Alzheimer’s disease. [13]
tectorial membrane
A membrane that sits atop the organ of Corti in the cochlear duct. See Figure 6.1. [6]
tectum
The dorsal portion of the midbrain consisting of the inferior and superior colliculi. [2]
tegmentum
The main body of the midbrain, containing the substantia nigra, periaqueductal gray, part of the reticular formation, and multiple fiber tracts. [2]
telencephalon
The anterior part of the fetal forebrain, which will become the cerebral hemispheres in the adult brain. See Figure 2.12, 13.24. Compare diencephalon. [2, 13]
temporal coding
Frequency discrimination in which the pitch of a sound is determined by the rate of firing of auditory neurons. Compare place coding. [6]
temporal lobe
The large lateral region of cortex in each cerebral hemisphere. It is continuous with the parietal lobe posteriorly and separated from the frontal lobe by the Sylvian fissure. See Figure 2.10. Compare occipital lobe. [2]
temporal resolution
The ability to track changes in the brain that occur very quickly. Compare spatial resolution. [14]
temporal summation
The summation of postsynaptic potentials that reach the axon hillock at different times. The closer in time the potentials occur, the more complete the summation is. See Figure 3.10. Compare spatial summation. [3]
temporoparietal junction (TPJ)
The point in the brain where the temporal and parietal lobes meet. It plays a role in shifting attention to a new location after target onset. [14]
TENS
See transcutaneous electrical nerve stimulation. [5]
testes (sing. testis)
The male gonads, which produce sperm and androgenic steroid hormones. See Figure 8.1. Compare ovaries. [8]
testosterone
A hormone, produced by male gonads, that controls a variety of bodily changes that become visible at puberty. It is one of a class of hormones called androgens. See Figure 8.13. [8, 11]
tetanus
An intense volley of action potentials. [13]
tetrahydrocannabinol (THC)
See delta-9-tetrahydrocannabinol. [4]
thalamus (pl. thalami)
The brain regions at the top of the brainstem that trade information with the cortex. See Figures 2.14, 2.15, 2.16. [2, 5]
THC
See delta-9-tetrahydrocannabinol. [4]
therapeutic index
The margin of safety for a given drug, expressed as the distance between effective doses and toxic doses. See Figure 4.6. [4]
thermoregulation
The active process of maintaining a constant internal temperature through behavioral and physiological adjustments. [9]
third ventricle
The midline ventricle that conducts cerebrospinal fluid from the lateral ventricles to the fourth ventricle. See Figure 2.17. Compare fourth ventricle and lateral ventricle. [2]
thoracic
Referring to the 12 spinal segments below the cervical (neck) portion of the spinal cord, corresponding to the chest. See Figures 2.8, 2.9. Compare cervical, lumbar, sacral, and coccygeal. [2]
threshold
The stimulus intensity that is just adequate to trigger an action potential in an axon. [3, 5]
thrombolytic
A substance that is used to unblock blood vessels and restore circulation. [ASF 15.5]
thyroid-stimulating hormone (TSH)
A tropic hormone, released by the anterior pituitary gland, that signals the thyroid gland to secrete its hormones. [ASF 8.3]
timbre
The characteristic sound quality of a musical instrument, as determined by the relative intensities of its various harmonics. See Box 6.1. [6]
tinnitus
A sensation of noises or ringing in the ears not caused by external sound. [6]
tip link
A fine, threadlike fiber that runs along and connects the tips of stereocilia. See Figure 6.3. [6]
TMS
See transcranial magnetic stimulation. [2]
tolerance
See drug tolerance. [4]
tonic receptor
A receptor in which the frequency of action potentials declines slowly or not at all as stimulation is maintained. Compare phasic receptor. [5]
tonotopic organization
A major organizational feature in auditory systems, in which neurons are arranged as an orderly map of stimulus frequency, with cells responsive to high frequencies located at a distance from those responsive to low frequencies. [6]
topographic projection
A mapping that preserves the point-to-point correspondence between neighboring parts of space. For example, the retina extends a topographic projection onto the cortex. [7]
Tourette’s syndrome
A disorder that is characterized by heightened sensitivity to tactile, auditory, and visual stimuli that may be accompanied by the buildup of an urge to emit verbal or phonic tics. See Box 12.2. [12]
TPJ
See temporoparietal junction. [14]
trace amine–associated receptor (TAAR)
Any one of a family of probable pheromone receptors produced by neurons in the main olfactory epithelium. TAARs are candidate pheromone receptors, despite being situated outside the vomeronasal organ. [6]
tract
A bundle of axons found within the central nervous system. Compare nerve. [2]
transcranial magnetic stimulation (TMS)
A noninvasive technique for examining brain function that applies strong magnetic fields to stimulate cortical neurons, in order to identify discrete areas of the brain that are particularly active during specific behaviors. Compare magnetoencephalography. [2]
transcript
See messenger RNA. [App]
transcription
The process during which mRNA forms bases complementary to a strand of DNA. The resulting message (called a transcript) is then used to translate the DNA code into protein molecules. See Appendix Figure A.2. Compare translation. [App]
transcutaneous electrical nerve stimulation (TENS)
The delivery of electrical pulses through electrodes attached to the skin, which excite nerves that supply the region to which pain is referred. [5]
transduction
The conversion of one form of energy to another, as converting light into neuronal activity. [6, 7]
transgenic
Referring to an animal in which a new or altered gene has been deliberately introduced into the genome. [App]
transient ischemic attack (TIA)
A temporary blood restriction to part of the brain that causes strokelike symptoms that quickly resolve, serving as a warning of elevated stroke risk. [2]
transient receptor potential 2 (TRP2)
A receptor, found in some free nerve endings, that opens its channel in response to rising temperatures. [5]
translation
The process by which amino acids are linked together (directed by an mRNA molecule) to form protein molecules. See Appendix Figure A.2. Compare transcription. [App]
transmitter
See neurotransmitter. [2, 3, 4]
transporter
A specialized membrane component that returns transmitter molecules to the presynaptic neuron for reuse. [3, 4]
transverse plane
See coronal plane. [2]
trichromatic hypothesis
A hypothesis of color perception stating that there are three different types of cones, each excited by a different region of the spectrum and each having a separate pathway to the brain. [7]
tricyclic antidepressant
An antidepressant that acts by increasing the synaptic accumulation of serotonin and norepinephrine. [4]
trinucleotide repeat
Repetition of the same three nucleotides within a gene, which can lead to dysfunction, as in Huntington’s disease. [ASF 5.5]
trophic factor
See neurotrophic factor. [13]
tropic hormone
Any of a class of anterior pituitary hormones that affect the secretion of hormones by other endocrine glands. See Figure 8.12. [8]
TRP2
See transient receptor potential 2. [5]
TSH
See thyroid-stimulating hormone. [ASF 8.3]
tuberomammillary nucleus
A region of the basal hypothalamus, near the pituitary stalk, that plays a role in generating stage 3 (slow wave) sleep. [10]
tuning curve
A graph of the responses of a single auditory nerve fiber or neuron to sounds that vary in frequency and intensity. See Figure 6.5. [6]
Turner’s syndrome
A condition, seen in individuals carrying a single X chromosome but no other sex chromosome, in which an apparent female has underdeveloped but recognizable ovaries. [8]
tympanic canal
See scala tympani. [6]
tympanic membrane
Also called eardrum. The partition between the external ear and the middle ear. See Figure 6.1. [6]
typical antipsychotic
Also called typical neuroleptic. An antischizophrenic drug that shows antagonist activity at dopamine D2 receptors. Compare atypical antipsychotic. [12]

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U

ultradian
Referring to a rhythmic biological event with a period shorter than a day, usually from several minutes to several hours long. Compare infradian. [10]
ultrasound
High-frequency sound; in general, above the threshold for human hearing, at about 20,000 Hz. Compare infrasound. [6]
umami
One of the five basic tastes—the meaty, savory flavor. (The other four tastes are salty, sour, sweet, and bitter.) [6]
unipolar neuron
Also called monopolar neuron. A nerve cell with a single branch that leaves the cell body and then extends in two directions; one end is the input zone, and the other end is the output zone. See Figure 2.3. Compare bipolar neuron and multipolar neuron. [2]
up-regulation
A compensatory increase in receptor availability at the synapses of a neuron. Compare down-regulation. [4]

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V

V1
See primary visual cortex. [7]
vagina
The opening from the outside of the body to the cervix and uterus in females. [8]
vagus nerve
Cranial nerve X, which provides extensive innervation of the viscera (organs). The vagus both regulates visceral activity and transmits signals from the viscera to the brain. See Figures 2.7, 9.15. [2, 9]
vasopressin
Also called arginine vasopressin or antidiuretic hormone. A peptide hormone from the posterior pituitary that promotes water conservation and increases blood pressure. [8, 9]
ventral
In anatomy, toward the belly or front of the body, or the bottom of the brain. See Box 2.2. Compare dorsal. [2]
ventral tegmental area (VTA)
A portion of the midbrain that projects dopaminergic fibers to the nucleus accumbens. [4]
ventricular system
A system of fluid-filled cavities inside the brain. See Figure 2.17. [2]
ventricular zone
Also called ependymal layer. A region lining the cerebral ventricles that displays mitosis, providing neurons early in development and glial cells throughout life. See Figure 13.25. [13]
ventromedial hypothalamus (VMH)
A hypothalamic region involved in sexual behaviors, eating, and aggression. See Figures 8.20, 9.12. [8, 9, 11]
vertex spike
A sharp-wave EEG pattern that is seen during stage 1 sleep. See Figure 10.9. [10]
vestibular canal
See scala vestibuli. See Figure 6.1. [6]
vestibular nucleus
A brainstem nucleus that receives information from the vestibular organs through cranial nerve VIII (the vestibulocochlear nerve). [6]
vestibular system
The sensory system that detects balance. It consists of several small inner-ear structures that adjoin the cochlea. [6]
vestibulocerebellum
The middle portion of the cerebellum, sandwiched between the spinocerebellum and the cerebrocerebellum and consisting of the nodule and the flocculus. It helps the motor systems to maintain posture and appropriate orientation toward the external world. [ASF 5.4]
vestibulocochlear nerve
Cranial nerve VIII, which runs from the cochlea to the brainstem auditory nuclei. See Figures 2.7, 6.1. [6]
visual acuity
Sharpness of vision. [7]
visual cortex
See occipital cortex. [7]
visual field
The whole area that you can see without moving your head or eyes. [7]
visual P1 effect
A positive deflection of the event-related potential, occurring 70–100 milliseconds after stimulus presentation, that is enhanced for selectively attended visual input compared with ignored input. Compare auditory N1 effect. [14]
VMH
See ventromedial hypothalamus. [8, 9, 11]
VNO
See vomeronasal organ. [6, 8]
voltage-gated Na+ channel
A Na+-selective channel that opens or closes in response to changes in the voltage of the local membrane potential. It mediates the action potential. Compare ionotropic receptor. [3]
voluntary attention
See endogenous attention. [14]
vomeronasal organ (VNO)
A collection of specialized receptor cells, near to but separate from the olfactory epithelium, that detect pheromones and send electrical signals to the accessory olfactory bulb in the brain. [6, 8]
vomeronasal system
A specialized sensory system that detects pheromones and transmits information to the brain. [6]
VTA
See ventral tegmental area. [4]

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W

Wada test
A test in which a short-lasting anesthetic is delivered into one carotid artery to determine which cerebral hemisphere principally mediates language. See Box 15.1. [15]
wavelength
The length between two peaks in a repeated stimulus such as a wave, light, or sound. See Figure 7.23. [7]
Wernicke-Geschwind model
See connectionist model of aphasia. [15]
Wernicke’s aphasia
See fluent aphasia. [15]
Wernicke’s area
A region of temporoparietal cortex in the brain that is involved in the perception and production of speech. See Figures 15.5, 15.6, 15.7. Compare Broca’s area. [15]
Western blot
A method of detecting a particular protein molecule in a tissue or organ by separating proteins from that source with gel electrophoresis, blotting the separated proteins onto nitrocellulose, and then using an antibody that binds, and highlights, the protein of interest. Compare Northern blot and Southern blot. [App]
white matter
A light-colored layer of tissue, consisting mostly of myelin-sheathed axons, that lies underneath the gray matter of the cortex. White matter mostly transmits information. See Figures 2.8, 2.11. Compare gray matter. [2]
Williams syndrome
A disorder characterized by impairments of spatial cognition and IQ but superior linguistic abilities. [15]
withdrawal symptom
An uncomfortable symptom that arises when a person stops taking a drug that he or she has used frequently, especially at high doses. [4]
within-participants experiment
An experiment in which the same set of individuals is compared before and after an experimental manipulation. The experimental group thus serves as its own control group. Compare between-participants experiment. [1]
wolffian duct
A duct system in the embryo that will develop into male reproductive structures (epididymis, vas deferens, and seminal vesicle) if androgens are present. See Figure 8.24. Compare müllerian duct. [8]
word blindness
A selective inability to understand written words. [15]
word deafness
1. A form of central deafness that is characterized by the specific inability to hear words, although other sounds can be detected. [6] 2. A selective inability to understand spoken words. [15]
working memory
See short-term memory. [13]

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Z

zeitgeber
Literally “time-giver” (in German). The stimulus (usually the light-dark cycle) that entrains circadian rhythms. [10]
zygote
The fertilized egg. [8]
Copyright 2015 Sinauer Associates
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