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Adolescent Psychopathology and the Developing BrainIntegrating Brain and Prevention Science$

Daniel Romer and Elaine F. Walker

Print publication date: 2007

Print ISBN-13: 9780195306255

Published to Oxford Scholarship Online: May 2009

DOI: 10.1093/acprof:oso/9780195306255.001.0001

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(p.475) Appendix A

(p.475) Appendix A


Adolescent Psychopathology and the Developing Brain

Shivali Dhruv

Oxford University Press

  1. Acetylation A process that introduces an acetyl radical (CH3CO) to an organic compound, occurring as a modification of proteins as part of the regulation of gene expression.

  2. ACTH (adrenocorticotropic hormone) A protein hormone of the anterior lobe of the pituitary gland that is part of the HPA stress response system, secreted in response to corticotropic releasing hormone (CRH), that stimulates the adrenal cortex to synthesize and release corticosteroids.

  3. Afferents Neurons or pathways that send signals to the CNS from the periphery or a higher processing system.

  4. Alpha 2 adrenergic receptor A postsynaptic, excitatory receptor that responds to binding of norepinephrine and epinephrine; activation causes various physiological reactions, including the stimulation of associated muscles and the constriction of blood vessels.

  5. Amphetamine An amine (organic compound with a nitrogen containing functional group) frequently abused as a stimulant of the central nervous system but used clinically, especially in the form of its sulfate, to treat attention deficit disorder and narcolepsy and formerly as a short-term appetite suppressant.

  6. (p.476)
  7. Amygdala A bilateral brain structure comprised of several nuclei that are specifically concerned with emotion, especially anxiety, and that coordinate the autonomic and endocrine responses to such emotional arousal. For anatomical localization, see Figure B1.

  8. Amygdalofugal neurons Neurons in one of the two major bundles of fibers connecting the amygdala with other areas of the brain; the two bundles of fibers are the stria terminalis and the ventral amygdalofugal pathway. The centromedial amygdala projects primarily to the lateral hypothalamus and brain stem through the ventral amygdalofugal tract, where it can influence hormonal and somatomotor aspects of behavior and emotional states.

  9. Analgesic A drug used to relieve pain, without the loss of consciousness.

  10. Anterior cingulated cortex The frontal part of the cingulated cortex that forms around the corpus collosum and plays a role in regulating heart rate and blood pressure, reward anticipation, decision making, empathy, and emotion.

  11. Anterior commisure A band of nerve fibers connecting the two hemispheres.

  12. Anterior pituitary An integral part of the endocrine system, under the influence of the hypothalamus, that produces and secretes peptide hormones that regulate physiological responses such as stress, growth, and reproduction. For brain localization, see Figure B1.

  13. Antidromic A nerve impulse or fiber conducting in a direction opposite to the norm in the local neural region.

  14. Appetitive (response) A response to a positively reinforcing stimulus.

  15. Apoptosis Programmed cell death that is a genetically determined normal physiological process of cell self-destruction to eliminate damaged or unwanted cells, marked by the fragmentation of nuclear DNA and activated by the presence or removal of a stimulus or suppressing agent. When halted, may result in uncontrolled cell growth and tumor formation.

  16. Arcuate fasciculus Thought to connect Broca’s area, involved in language processing, speech production, and comprehension, to Wernicke’s area, crucial to understanding and comprehending spoken language.

  17. Atypical antipsychotics Medications typically used as the first line of treatment for schizophrenia, favored over the typical antipsychotics for their decreased propensity (p.477) to cause extrapyramidal side (EPS) effects, various movement abnormalities as a consequence of dopamine antagonism, and an absence of sustained pro-lactin elevation (see D FENFLURAMINE). These agents may also be used for acute mania, bipolar mania, and psychotic agitation.

  18. Barbiturates A class of hypnotic drugs that increases chloride current by binding to postsynaptic GABA A receptors, thereby enhancing inhibitory synaptic transmission. They can function as sedatives and anticonvulsants and are often used recreationally for their state of intoxication, very similar to alcohol-induced intoxication. Although many individuals have safely taken barbiturates, concern about the addiction potential and fatalities associated with them led to the therapeutic use of alternative medications, mainly BENZODIAZEPINES.

  19. Basal ganglia A brain region that includes the caudate, putamen, globus pallidus and substantia nigra, all bilateral structures that together participate in the regulation of motor function. For brain localization, see Figure B2.

  20. Benzodiazepines A class of muscle relaxants, hypnotics, anticonvulsants, and antianxiety drugs that increases chloride conductance via binding to the GABA A receptor, thereby enhancing synaptic activity. Because of the high degree of negative side effects with barbiturates, benzodiazepines (BZDs) are used more commonly for clinical application. The advantages of BZDs are that there is a greater dose margin between anxioloysis (a state of minimal sedation) and full sedation, lower tolerance and dependence, and less potential for abuse.

  21. Binding Referring to the process of a LIGAND connecting to its RECEPTOR.

  22. Brainstem A stalk of the brain below the cerebral hemispheres, comprised of the medulla oblongata, pons, and midbrain. The brainstem serves as a major communication route between the forebrain, spinal cord, and peripheral nerves and is responsible for processing sensation, such as hearing and taste, and controlling balance. For anatomical localization, see Figure B1.

  23. Catecholamines Any of various water-soluble amines that are derived from ty-rosine and that function as hormones, neurotransmitters, or both. The most abundant catecholamines are epinephrine (adrenaline), NOREPINEPHRINE (noradrenaline), and DOPAMINE. High catecholamine levels are generally associated with stress and cause physiological changes in the body in preparation for the fight or flight response.

  24. Caudate nucleus A C-shaped structure in each cerebral hemisphere that comprises a mass of GRAY MATTER in the corpus striatum and is involved in the control of voluntary movement. For anatomical localization, see Figure B2.

  25. (p.478)
  26. cDNA array (complementary DNA array) A procedure used to identify DNA samples in gene expression analyses; complementary DNA is synthesized from and complementary to a given RNA strand. A microarray uses a glass or plastic solid structure, onto which single-stranded cDNA fragments attach and serve as probes.

  27. Cerebellum A brain structure that plays an important role in the integration of sensory input and motor output, specifically involved in the learning of motor skills and modulating force and range of movement.

  28. Cholinergic transmission Synaptic transmission produced by a neuron that releases acetylcholine.

  29. Chromatin A complex of nucleic acid and basic proteins (HISTONES) in the nucleus of cells that is condensed into chromosomes. Packaging into a chromatin structure constrains the size of the DNA molecule and allows the cell to control the expression of genes.

  30. Commisurotomy A surgical procedure used in epilepsy, severing the corpus collosum and anterior commisure, to prevent spread of epilepsy to the unaffected hemisphere.

  31. Consolidation The process by which recent memories are crystallized into long-term memory; can refer to molecular consolidation, requiring protein synthesis, or network consolidation, as initial memory storage in the hippocampus is slowly moved into the neocortex.

  32. Corpus collosum The largest commissure and white matter structure in the brain, connecting the two cerebral hemispheres; serves as the main communication route between the left and right halves of the brain.

  33. Corticotrophin releasing hormone/factor (CRH/CRF) A polypeptide hormone and neurotransmitter secreted by the paraventricular nucleus of the hypothalamus that regulates the release of ACTH by the anterior lobe of the pituitary gland.

  34. Cortisol A GLUCOCORTICOID hormone produced by the adrenal cortex upon stimulation by ACTH that mediates various metabolic processes, has antiinflam-matory and immunosuppressive properties, and is most importantly involved in the stress response in human and nonhuman primates (in subprimates, the main glucocorticoid hormone is corticosterone).

  35. CSF (cerebrospinal fluid) A clear bodily fluid that is secreted from blood into the lateral ventricles of the brain and spinal chord; is involved in the mechanical protection of the brain, distribution of neuroendocrine factors, the facilitation of (p.479) pulsatile cerebral blood flow, and the maintenance of uniform pressure within the brain and spinal cord.

  36. Cyclothymia A chronic, low-level form of bipolar disorder that consists of short periods of mild depression alternating with short periods of hypomania.

  37. Declarative memory The aspect of memory that stores facts, objects, and events and can be divided into two types: episodic, or knowledge about events in a person’s past, and semantic, or knowledge of the meaning of words. Can be contrasted with procedural memory, which stores skills and operations.

  38. Decussation The crossing of a neuronal pathway from one side of the body to the contralateral side.

  39. Depolarization Excitation or decrease in the membrane potential of the POSTSYN-APTIC cell increasing the likelihood that a neuron will generate an action potential.

  40. Dexamethasone challenge A procedure designed to assess function of the hy-pothalamic pituitary adrenal axis; involves the administration of the synthetic steroid, dexamethasone, followed by measurement of cortisol levels to obtain the test results.

  41. d fenfluramine challenge A procedure in which d fenfluramine stimulates the release of SEROTONIN and acts as a potent inhibitor of the reuptake of serotonin into the nerve terminal. The prolactin response to d fenfluramine challenge has been used to assess serotonergic function and appears to be blunted in depressed patients.

  42. Diffusion tensor imaging An MRI based technique that allows the visualization of location, orientation, and the anisotropy (being directionally dependent or having different characteristics depending on the specific direction) of the brain’s WHITE MATTER tracts.

  43. Dopamine A catecholamine neurotransmitter found abundantly in the brain; is thought to play a role in Parkinson’s disease and has important functions in the learning of novel stimuli, the experience of pleasure, the development of substance abuse and in the neural functioning of psychosis.

  44. Dopamine receptors A class of metabotropic G protein-coupled receptors with dopamine as their endogenous LIGAND.

  45. D1-like receptor Members of this family include the D1 and D5 dopamine receptors that tend to have excitatory actions.

  46. (p.480)
  47. D2-like receptor Members of this family include the D2, D3, and D4 dopam-ine receptors that tend to have inhibitory actions.

  48. EEG (electroencephalography) The neurophysiologic, often diagnostic, measurement of the electrical activity of the brain using recording equipment attached to the scalp by electrodes.

  49. Efferents Neurons or pathways that send signals from the central nervous system to the periphery or a lower processing system.

  50. Electrophysiology A branch of physiology pertaining to the relationship between ion flow and its regulation; when speaking specifically of the brain, it includes measurements of the electrical activity of neurons, specifically action potentials.

  51. Encoding The process of transforming or recoding initial information into the memory system for later retrieval.

  52. Epigenesis Theory that an individual is developed by successive differentiation of an unstructured egg and that the embryo is not preformed. This definition has been expanded to other fields of medicine, and in psychiatry, generally refers to the occurrence of secondary symptoms as a result of disease. In genetics, epigenetic effects refer to the interaction between environmental and genetic factors in gene expression.

  53. Executive function A theorized cognitive system that mediates processes such as abstract thinking, cognitive flexibility, the planning of complex behaviors, rule acquisition, and personality expression, and that moderates social behavior by inhibiting inappropriate actions and irrelevant sensory information.

  54. Extinction The process by which learned associations are actively lost.

  55. fMRI (functional magnetic resonance imaging) The use of magnetic resonance imaging (MRI) to learn which regions of the brain are active during a specific function by measuring the haemodynamic (blood flow) response related to neural activity.

  56. Frontal cortex or lobe A brain region present in the front of each hemisphere in all vertebrates; controls movements of specific body parts and is involved in impulse control, judgment, language, memory, problem solving, sexual behavior, socialization, spontaneity and planning, and coordinating and controlling executive function. For subregions, see ORBITOFRONTAL CORTEX and PREFRONTAL CORTEX.

  57. GABA (gamma-aminobutyric acid) The major inhibitory neurotransmitter that tends to have relaxing, antianxiety and anticonvulsive effects.

  58. (p.481)
  59. GABA A receptor A type of GABA receptor that is found ubiquitously in the CNS.

  60. Glial cells Commonly referred to as neuroglia, or just glia, the nonneouronal cells in the nervous system that maintain homeostasis, form the myelin sheath around neurons, provide support and nutrition, and have important developmental roles. Recent findings indicate that they are active participants in synaptic transmission, and may be more crucial then previously thought.

  61. Glucocorticoid A hormone that affects the metabolism of carbohydrates, fats, and proteins, regulates cardiovascular and homeostatic functions, acts as an anti-inflammatory, immunosuppressive agent that is crucial to the stress response. Glucocorticoids are made in the adrenal gland and chemically classified as steroids; cortisol is the major natural glucocorticoid in primates.

  62. Glutamate The major excitatory neurotransmitter and a common amino acid.

  63. Gray matter One of two main solid components of the CNS, consisting of nerve cell bodies and the nonmylelinated sections of axons and dendrites, crucial for information processing.

  64. Habituation A form of nonassociative learning in which there is a gradual attenuation of the behavioral response with repetition of an innocuous stimulus.

  65. Hippocampus A bilateral brain structure located in the temporal lobe and an integral part of the limbic system that plays an important role in aspects of declarative memory. It is also implicated in disorders such as amnesia, Alzheimer’s disease, schizophrenia, and various mood disorders. For localization, see Figure B1.

  66. Histone Small, basic proteins found in the nuclei of the cells of most organisms, other than viruses and bacteria (eukaryotic cells); the chief proteins of CHROMATIN, playing a role in gene regulation and acting as spools around which DNA winds.

  67. Homologous A likeness because of shared ancestry.

  68. HPA (hypothalamic pituitary adrenal) axis A neural system activated by stress that governs a neurohormonal cascade that has pervasive effects on brain function. Activation of the HPA axis leads to subsequent release of CORTICOTROPHIN RELEASING HORMONE (CRH) from the HYPOTHALAMUS, ADENOCORTICOTROPIC HORMONE (ACTH) from the pituitary, and GLUCOCORTICOIDES from the adrenals. (p.482) The HPA axis also modulates cardiovascular function, immunity, fluid retention, and metabolism.

  69. Hypophyseal portal system The system of blood vessels that supplies blood to part of the hypothalamus and the anterior pituitary, allowing endocrine communication between the two structures.

  70. Hypoplasia Underdevelopment or incomplete development of a tissue or organ. Hypoplasia is less drastic than aplasia, in which there is no development at all.

  71. Hypothalamus The ventral region of the diencephalon that regulates autonomic, endocrine, and visceral functions. For anatomical localization, see Figure B1.

  72. Internal capsule A massive layer (8- to 10-mm thick) of WHITE MATTER that serves as a major route by which the cerebral cortex is connected with the brainstem and spinal cord. It is a V-shaped structure, divided into the genu, anterior limb, posterior limb, and retrolenticular and sublenticular portions.

  73. Interneuron One of the major functional types of neurons; these relay neurons communicate only with other neurons and provide inhibitory connections between sensory and motor neurons, as well as between themselves.

  74. Intracerebroventricular (ICV) For research purposes, describing injection into the cerebral ventricles of the brain.

  75. Intracranial self-stimulation A procedure in which electrodes are implanted into an animal’s brain that are activated by the animal’s voluntary pressing of a lever. This demonstrated that although stimulation in most sites of the brain is not reinforcing, when DOPAMINE is involved, presumably in reward pathways, reinforcement of the behavior occurred.

  76. Ligand An extracellular substance, typically referring to a transmitter, drug, or hormone, that binds to an ion channel or a POSTSYNAPTIC receptor. This binding leads to a conformational change, or change in the physical structure, that subsequently alters the cell’s response.

  77. Limbic system A collective term for the structures involved in learning, memory, motivation, and emotion. These brain regions include the amygdala, cingulate gyrus, fornicate gyrus, hippocampus, hypothalamus, mammillary body, nucleus accumbens, orbitofrontal cortex, and parahippocampal gyrus. For brain localizations, see Figure B1.

  78. (p.483)
  79. LTP (long-term potentiation) The long-lasting strengthening of a connection between two nerve cells.

  80. Medial preoptic area (MPOA) Region of the brain that is situated immediately below the anterior commissure, above the optic chiasma, and anterior to the hypothalamus, and that regulates certain autonomic activities often with the hypothalamus.

  81. Mediators Processes that act as an intermediary agent; used to describe variables that mediate the effect of one factor on another.

  82. Mesencephalic reticular activating system Situated at the core of the brain stem, the reticular activating system is believed to be the center of arousal and motivation in animals, involved in circadian rhythm, and affected by psychotro-pic drugs and anesthetics.

  83. Methylation The enzymatic introduction of a methyl group (CH3) in a chemical compound; involved in the regulation of gene expression, regulation of protein function, epigenetic inheritance, embryonic development, and RNA metabolism.

  84. Methylphenidate A mild stimulant of the central nervous system that is administered orally to treat narcolepsy and hyperactivity disorders.

  85. Microcephaly A condition in which the circumference of the head is abnormally small, usually associated with mental retardation.

  86. Microgenesis A theory of mind and brain based on a process approach to anatomy in relation to patterns of symptom formation in patients with disturbances of language, action, and perception. A model of the organization of cognition in the normal brain that is inferred from the symptoms of brain damage, their change over time, and their relation to pathology in specific brain areas.

  87. Midbrain Region including the inferior and superior colliculi, the cerebral peduncles, internal capsule, cerebral aqueduct, and substantia nigra; controls many sensory and motor functions.

  88. Moderator In statistics, a variable that changes the direction or strength of the association between two other variables.

  89. Monoamines Amines, specifically neurotransmitters and neuromodulators, that are functionally important in neural transmission, that have one organic substituent (p.484) attached to the nitrogen atom. These include catecholamines (dopamine, norephine-phrine, and epinephrine), serotonin, histamine, thyronamines, tryptamine, tyramine, and β-Phenylethylamine.

  90. mRNA (messenger RNA) An RNA, produced by transcription, that encodes and carries genetic information from nuclear DNA to ribosomes, the site of protein synthesis.

  91. Myelin sheath An electrically insulating phospholipid layer surrounding the axons of neurons performed by glial cells; helps to speed transmission of information.

  92. Neocortex The large six-layered dorsal region of the cerebral cortex that is unique to mammals.

  93. Neurogenesis The process by which neurons are created and therefore extremely prominent during prenatal development to populate the growing brain. Recent findings show that this early developmental phenomenon also occurs in certain regions (dentate gyrus and olfactory bulb) in adulthood.

  94. Neuropeptides Endogenous peptides (as endorphins or enkephalins) that serve as a chemical signal to influence neural activity or functioning.

  95. Neuroplasticity The brain’s ability to physically change in response to stimuli and activity; thought to be the neural mechanism of learning.

  96. Neurotoxin A protein complex that is specifically poisonous to neurons, usually by interacting with membrane proteins and ion channels.

  97. Neurotransmitter Any of several chemical substances released by PRESYNAP-TIC neurons that relay, modulate, and amplify electrical signals by binding to POSTSYNAPTIC receptors. A neurotransmitter must be synthesized endogenously (originating from within the neuron) and be available in amounts sufficient to exert effects on POSTSYNAPTIC neurons. A biochemical mechanism for its inactivation must also be present, as the neurotransmitter must be physically inactivated after it exerts its effects. The final defining factor of a neurotransmitter is that systemic administration (superficially adding it) should mimic the endogenous effects. Examples include: (1) amino acids (primarily glutamic acid, GABA, aspartic acid, and glycine), (2) peptides (vasopressin, somatostatin, neurotensin, etc.), and (3) monoamines (norepinephrine, dopamine, and serotonin) plus acetylcholine.

  98. NMDA receptor A type of GLUTAMATE receptor that is activated by NMDA (N-methyl-D-aspartate) and is thought to play a critical role in synaptic plasticity, the cellular mechanism for learning and memory.

  99. (p.485)
  100. Noradrenergic transmission Synaptic transmission produced by a neuron that releases norepinephrine.

  101. Norepinephrine A CATECHOLAMINE that is the chemical means of transmission across synapses in postganglionic neurons of the sympathetic nervous system and in some parts of the central nervous system. It is a vasopressor hormone of the adrenal medulla, has a prominent role in the stress response, is important in attention, and is a precursor of epinephrine in its major biosynthetic pathway.

  102. Nucleotides Basic structural units of DNA and RNA consisting of a ribose or deoxyribose sugar joined to a heterocyclic base and to a phosphate group that play important roles in energy production, metabolism, and signaling.

  103. Nucleus accumbens A collection of neurons that are part of the ventral stria-tum and thought to play an important role in reward, pleasure, and addiction. For localization see Figure B1.

  104. Ontogenetic The development or course of development of an individual organism.

  105. Opiate A drug derived from opium, tending to induce sleep and to work as an analgesic.

  106. Orbitofrontal cortex (OFC) A region of the medial PFC above the eyes important in decision making, emotion, and in the regulation of planning behavior associated with reward and punishment.

  107. Oxytocin A hormone that also acts as a neurotransmitter, secreted by the anterior lobe of the pituitary gland, that stimulates the contraction of uterine muscle and the secretion of milk, is released during orgasm, and is involved in social recognition and pair bonding.

  108. Parietal lobe The middle division of each cerebral hemisphere that is situated behind the central sulcus, above the sylvian fissure, and in front of the parieto-occipital sulcus and is crucial in the integration of sensory information and in the manipulation of objects.

  109. Parvocellular Characterized by relatively small cell bodies.

  110. Phencyclidine (PCP) A former medical and veterinary anesthetic, now often used illicitly as a psychedelic drug to induce hallucinogenic effects.

  111. (p.486)
  112. Polymorphism The existence of a gene or molecule in two or more forms in a single species.

  113. Postsynaptic cell A neuron whose excitability is affected by chemical or electrical signals in the synapse sent from a presynaptic cell.

  114. Prefrontal cortex (PFC) The gray matter of the anterior part of the frontal lobe that is highly developed in humans and plays a role in the regulation of complex cognitive, emotional, and behavioral functioning (executive function), including personality expression and moderating social behavior. The PFC includes the medial PFC and dorsolateral PFC. For anatomical localization, see Figure B1.

  115. Presynaptic cell The communicating cell that secretes the neurotransmitter, which binds to receptors on the postsynaptic cell.

  116. Promoter A regulatory region of DNA sequence, usually immediately upstream from the coding region, that enables the gene to be transcribed.

  117. Propagule The seed in sexual reproduction.

  118. Prophylactic A preventative, such as a drug, to impede the spread or incidence of a disease or infection.

  119. Pruning Elimination of axons to eradicate projections to inappropriate targets and to enhance the specificity of axonal projections.

  120. Putamen A portion of the basal ganglia that forms the outermost part of the lenticular nucleus that plays an important role in reinforcement learning. For anatomical localization, see Figure B2.

  121. PVN (paraventricular nucleus) A discrete band of nerve cells in the anterior part of the hypothalamus that contain centrally projecting peptide neurons and both magnocellular (that produce vasopressin and oxytocin) and parvocellular (that produce CRH, vasopressin, and TRH) neurosecretory cells.

  122. Pyramidal neuron A multipolar neuron located in the hippocampus and cerebral cortex that has a triangular-shaped soma, with both apical and basal dendrites. These neurons use GLUTAMATE as the neurotransmitter and make excitatory connections, as opposed to the inhibitory INTERNEURONS that use GABA.

  123. Receptor A protein on the cell membrane or within the cytoplasm or cell nucleus, characterized by the specific, high affinity binding of a LIGAND in a lock-and-key (p.487) fashion. BINDING transmits the extracellular signal and triggers specific physiological events within the POSTSYNAPTIC cell.

  124. Reversal potential The membrane voltage at which there is no net flow of ions from one side of the membrane to the other.

  125. Serotonin (5 hydroxytryptamine) A monoamine neurotransmitter that is a powerful vasoconstrictor and is found in the brain, blood serum, and gastric mucous membrane of mammals. In the CNS, serotonin is thought to play a major role in regulation of mood, sleep, emesis, sexuality, and appetite, and is implicated in the pathophysiology of many disorders, such as depression, migraines, bipolar disorder, and anxiety.

  126. 5 HT (serotonin) receptor A receptor of serotonin, as well as a broad range of pharmaceutical and hallucinogenic drugs such as antidepressants, anxiolytics, and antoemetics. There are many subtypes (5 HT1A, 5 HT1B, 5 HT1D, 5 HT2A, 5 HT2B, 5 HT2C, 5 HT3, 5 HT4, 5 HT5, 5 HT6, 5 HT7) of this receptor that all have different actions, agonists, and antagonists.

  127. Serotonin transporter A MONOAMINE TRANSPORTER protein that regulates the serotonin concentration in the synapse by recycling serotonin back into the neuron. SSRIs (selective serotonin reuptake inhibitors) reduce binding of serotonin to the transporter, increasing its time and therefore effect in the synaptic cleft, and are used to treat depression and OCD.

  128. Signal transduction Any process, taking a millisecond or as long as a few seconds, by which a cell converts one kind of signal or stimulus into another, often involving a sequence of biochemical reactions inside the cell that are carried out by enzymes and linked through second messengers.

  129. Spatial resolution The ability to sharply and clearly define the extent or shape of features within an image, describing how close two features can be and still be resolved as unique.

  130. Steroid hormones Any of numerous hormones (such as glucocorticoids, min-eralocorticoids, androgens, estrogens, and progestogens) having the characteristic ring structure of steroids and formed in the body from cholesterol.

  131. Striatum A subcortical brain structure, consisting of the caudate nucleus and the putamen, that plays important roles in planning and modulating movement pathways and other cognitive processes involving executive function. See Figure B2.

  132. (p.488)
  133. Substance P A neuropeptide and neurotransmitter that is widely distributed in the brain, spinal cord, and peripheral nervous system that acts across nerve synapses to produce prolonged postsynaptic excitation. In the CNS, substance P is important in regulating mood disorders, anxiety, stress, reinforcement, neurogenesis, neurotoxicity, emesis, and pain.

  134. Subunit A single protein molecule that assembles with other protein molecules to form a multimeric (formed with many different subunits) or oligomeric (composed of many identical subunits) protein. A subunit is made up of one polypep-tide chain, the sequence specifics of which are stored in the code of genes.

  135. Sulcus A groove between two gyri in the cerebral cortex.

  136. Sympathetic adrenal medullary (SAM) The adrenal medulla, the principal site of catecholamine synthesis, is actually a ganglion, a tissue mass that contains the dendrites and cell bodies of neurons, of the sympathetic nervous system.

  137. Synaptogenesis The formation of nerve synapses.

  138. Telencephalon The anterior-most embryological region of the brain that gives rise to the cerebral hemispheres and other, smaller structures within the brain.

  139. Thalamus Located in the center of the brain, serves as a relay station for nerve impulses carrying sensory information into the central nervous system and processes most of the information reaching the cerebral cortex. For localization, see Figures B1 and B2.

  140. Transcription The process of using a DNA molecule as a template to enzymati-cally construct a complementary messenger RNA molecule, thereby transferring genetic information.

  141. Transcription factors Any of various proteins that bind to DNA at specific promoter or enhancer regions to regulate gene expression by enhancing transcription.

  142. Transporter A protein that mediates the active transport of ions, nutrients, and other molecules into a cell against their electrochemical gradient by using energy from ATP hydrolysis, a reaction in which chemical energy stored in the form of phosphate bonds in ATP (adenosine triphosphate) is released.

  143. Trinucleotide repeat sequences Stretches of DNA in a gene that contain the same trinucleotide sequence repeated many times and occur throughout all ge-nomic sequences. However, if the repeat is present in a gene, an expansion of the repeats may result in a defective gene product that can often lead to disease states.

  144. (p.489)
  145. Typical antipsychotics Medications used to treat psychosis, especially schizophrenia, acute mania, and agitation; are thought to work by blocking dopamine receptors and are now being replaced by atypical antipsychotic drugs.

  146. Vasopressin (arginine) A polypeptide hormone, also known as antidiuretic hormone (ADH), that is secreted by the posterior lobe of the pituitary gland, increases blood pressure, and exerts an antidiuretic effect. Like OXYTOCIN, vasopressin is thought to play a role is social behaviors, such as pair bonding.

  147. Ventricle A cavernous system within the brain that produces cerebrospinal fluid (CSF), used to bathe and cushion the brain and spinal cord.

  148. White matter One of the two main solid components of the CNS, composed of myelinated axons that connect gray matter systems and carry nerve impulses between neurons; plays a crucial role in speeding information transmission.