All these definition are based on APA Dictionary. We have selected some terms here and you may find more at


'an almond-shaped structure in the temporal lobe that is a component of the limbic system and considered part of the basal ganglia. It comprises two main groups of nuclei—the corticomedial group and the basolateral group—and through widespread connections with other brain areas has numerous viscerosensory and autonomic functions as well as an important role in memory, emotion, perception of threat, and fear learning. Also called amygdaloid body; amygdaloid complex; amygdaloid nuclei.' - APA

Art Therapy

'the use of artistic activities, such as painting and clay modeling, in psychotherapy and rehabilitation. The process of making art is seen as healing, an experience that provides the opportunity to express oneself imaginatively, authentically, and spontaneously; over time, this process can lead to personal fulfillment, emotional reparation, and transformation. The products made in art therapy are seen as a means of symbolic communication and a vehicle for developing new insights and understandings, resolving conflicts, solving problems, and formulating new perceptions to achieve positive changes, growth, and rehabilitation.' - APA


'in front of or toward the front. In reference to two-legged upright animals, this term is sometimes used interchangeably with ventral to mean toward the front surface of the body. ' - APA


'a chemical compound that contains one or more amino groups (–NH2). Several neurotransmitters are amines, including acetylcholine, norepinephrine, and serotonin.' - APA

Acute Stress Disorder

'a disabling psychological condition that can occur immediately after exposure to a traumatic stressor. Symptoms such as intrusive thoughts, hyperarousal, and avoidance of situations that recall the traumatic event are the same as those of posttraumatic stress disorder but do not last longer than 4 weeks. This disorder may also include elements of dissociation, such as depersonalization and derealization.' - APA

Abnormal Psychology

'the branch of psychology devoted to the study, assessment, treatment, and prevention of maladaptive behavior. ' - APA

Action Potential (AP)

'the change in electric potential that propagates along the axon of a neuron during the transmission of a nerve impulse or the contraction of a muscle. It is marked by a rapid, transient depolarization of the cell’s plasma membrane, from a resting potential of about –70 mV (inside negative) to about +30 mV (inside positive), and back again, after a slight hyperpolarization, to the resting potential. Each action potential takes just a few milliseconds. Also called spike potential.' -APA

Amino Acid

'an organic compound that contains an amino group (–NH2) and a carboxyl group (–COOH). Twenty amino acids are constituents of proteins; nine of these are essential amino acids, that is, they cannot be synthesized by the body and must be obtained from foods. Other amino acids (e.g., glutamic acid, glycine) are neurotransmitters or precursors to neurotransmitters.' - APA


'attention-deficit/hyperactivity disorder. a behavioral syndrome characterized by the persistent presence of six or more symptoms involving (a) inattention (e.g., failure to complete tasks or listen carefully, difficulty in concentrating, distractibility) or (b) impulsivity or hyperactivity (e.g., blurting out answers; impatience; restlessness; fidgeting; difficulty in organizing work, taking turns, or staying seated; excessive talking; running about; climbing on things). The symptoms, which impair social, academic, or occupational functioning, start to appear before the age of 7 and are observed in more than one setting. ADHD has been given a variety of names over the years, including the still commonly used attention-deficit disorder (ADD)' - APA

Avoidant Personality Disorder

'a personality disorder characterized by (a) hypersensitivity to rejection and criticism, (b) a desire for uncritical acceptance, (c) social withdrawal in spite of a desire for affection and acceptance, and (d) low self-esteem. This pattern is long-standing and severe enough to cause objective distress and seriously impair the ability to work and maintain relationships. It is included in both DSM–IV–TR and DSM–5. [first defined in 1969 by Theodore Millon]' - APA


'the long, thin, hollow, cylindrical extension of a neuron that normally carries a nerve impulse away from the cell body. An axon often branches extensively and may be surrounded by a protective myelin sheath. Each branch of an axon ends in a terminal button (also called synaptic bouton or knob, among numerous other synonyms) from which an impulse is transmitted, through discharge of a neurotransmitter, across a synapse to a neighboring neuron. Also called nerve fiber.' - APA

Arachnoid Matter

'the middle one of the three membranous layers (meninges) covering the surface of the brain and spinal cord, so called because its strands of tissue resemble spiders’ webs. Also called arachnoid; arachnoid membrane.' -APA

Acetylcholine (ACh)

'a major, predominantly excitatory but also inhibitory, neurotransmitter both in the central nervous system, where it plays an important role in memory formation and learning and is implicated in Alzheimer’s disease, and in the peripheral nervous system, where it mediates skeletal, cardiac, and smooth muscle contraction and is implicated in myasthenia gravis and other movement disorders.' - APA


'an emotion characterized by apprehension and somatic symptoms of tension in which an individual anticipates impending danger, catastrophe, or misfortune. The body often mobilizes itself to meet the perceived threat: Muscles become tense, breathing is faster, and the heart beats more rapidly. Anxiety may be distinguished from fear both conceptually and physiologically, although the two terms are often used interchangeably. Anxiety is considered a future-oriented, long-acting response broadly focused on a diffuse threat, whereas fear is an appropriate, present-oriented, and short-lived response to a clearly identifiable and specific threat.' - APA

Autonomic Nervous System (ANS)

'the portion of the nervous system innervating smooth muscle and glands, including the circulatory, digestive, respiratory, and reproductive organs. It is divided into the sympathetic nervous system and parasympathetic nervous system. Autonomic responses typically involve changes in involuntary bodily functions, such as heart rate, salivation, digestion, perspiration, pupil size, hormone secretion, bladder contraction, and engorgement of the penis and clitoris. The system is called autonomic because it was once thought to function independently of the central nervous system.' -APA


'in front of or toward the front. In reference to two-legged upright animals, this term is sometimes used interchangeably with ventral to mean toward the front surface of the body. ' - APA

Association Fiber

'an axon from any of various neurons that link different parts of the same cerebral hemisphere.' - APA

Autism Spectrum Disorder (ASD)

'any one of a group of disorders with an onset typically occurring during the preschool years and characterized by varying but often marked difficulties in communication and social interaction. ASD was formerly said to include such disorders as the prototype autism, Asperger’s disorder, childhood disintegrative disorder, and Rett syndrome; it was synonymous with pervasive developmental disorder but more commonly used, given its reflection of symptom overlap among the disorders. It is now the official term used in DSM–5, where it encompasses and subsumes these disorders: Autism, Asperger’s disorder, and childhood disintegrative disorder are no longer considered distinct diagnoses, and medical or genetic disorders that may be associated with ASD, such as Rett’s syndrome, are identified only as specifiers of the disorder. Also called autistic spectrum disorder.' - APA

Behavioral Psychology

'the branch of psychology devoted to the study, assessment, treatment, and prevention of maladaptive behavior. ' - APA

Basolateral Group

'one of the two main groups of nuclei in the amygdala within the brain and the largest portion of the amygdaloid complex. Its nuclei receive neuromodulatory input from various neurotransmitter systems in the basal forebrain and brainstem, are connected particularly with higher order sensory and limbic association areas, and project to the central amygdala. They are implicated in fear conditioning and emotional learning. Also called basolateral complex.' - APA

Borderline Personality Disorder

'in DSM–IV–TR and DSM–5, a personality disorder characterized by a long-standing pattern of instability in mood, interpersonal relationships, and self-image that is severe enough to cause extreme distress or interfere with social and occupational functioning. Among the manifestations of this disorder are (a) self-damaging behavior (e.g., gambling, overeating, substance use); (b) intense but unstable relationships; (c) uncontrollable temper outbursts; (d) uncertainty about self-image, gender, goals, and loyalties; (e) shifting moods; (f) self-defeating behavior, such as fights, suicidal gestures, or self-mutilation; and (g) chronic feelings of emptiness and boredom.' - APA


'the science that deals with the biological basis of behavior, thoughts, and emotions and the reciprocal relations between biological and psychological processes. It also addresses topics such as behavior-changing brain lesions, chemical responses in the brain, and brain-related genetics. It includes such fields as behavioral neuroscience, clinical neuroscience, cognitive neuroscience, behavioral endocrinology, and psychoneuroimmunology. Also called biological psychology; physiological psychology; psychobiology.' - APA

Biopolar Neuron

'a neuron with only two extensions—an axon and a dendrite—that run from opposite sides of the cell body. Cells of this type are found primarily in the retina and also elsewhere in the nervous system. Also called bipolar cell.' - APA

Behavior Therapy

'a form of psychotherapy that applies the principles of learning, operant conditioning, and classical conditioning to eliminate symptoms and modify ineffective or maladaptive patterns of behavior. The focus of this therapy is upon the behavior itself and the contingencies and environmental factors that reinforce it, rather than exploration of the underlying psychological causes of the behavior. A wide variety of techniques are used in behavior therapy, such as behavior rehearsal, biofeedback, modeling, and systematic desensitization. Also called behavioral psychotherapy; conditioning therapy.' - APA

Broca's Area

'a region of the posterior portion of the inferior frontal convolution of a cerebral hemisphere that is associated with the production of speech. It is located on the left hemisphere of right-handed and of most left-handed individuals. [discovered in the 1860s and studied and researched by Paul Broca]' - APA

Basal Ganglia

'a group of nuclei (neuron cell bodies) deep within the cerebral hemispheres of the brain that includes the caudate nucleus, putamen, globus pallidus, substantia nigra, and subthalamic nucleus. The putamen and globus pallidus are together known as the lenticular (or lentiform) nucleus, the lenticular nucleus and caudate nucleus are together known as the corpus striatum, and the caudate nucleus and putamen are together called the striatum. The basal ganglia are involved in the generation of goal-directed voluntary movement. Also called basal nuclei.' - APA

Bipolar Disorder

'any of a group of mood disorders in which symptoms of mania and depression alternate. In DSM–IV–TR and DSM–5, the group includes primarily the following subtypes: bipolar I disorder, in which the individual fluctuates between episodes of mania or hypomania and major depressive episodes or experiences a mix of these: bipolar II disorder, in which the individual fluctuates between major depressive and hypomanic episodes; and cyclothymic disorder. The former official name for bipolar disorders, manic-depressive illness, is still in frequent use.' - APA

Cognitive Psychology

'the branch of psychology that explores the operation of mental processes related to perceiving, attending, thinking, language, and memory, mainly through inferences from behavior. The cognitive approach, which developed in the 1940s and 1950s, diverged sharply from contemporary behaviorism in (a) emphasizing unseen knowledge processes instead of directly observable behaviors and (b) arguing that the relationship between stimulus and response was complex and mediated rather than simple and direct. Its concentration on the higher mental processes also contrasted with the focus on instincts and other unconscious forces typical of psychoanalysis. More recently, cognitive psychology has been influenced by approaches to information processing and information theory developed in computer science and artificial intelligence. See also cognitive science.' - APA

Counseling Psychology

'the branch of psychology that specializes in facilitating personal and interpersonal functioning across the lifespan. Counseling psychology focuses on emotional, social, vocational, educational, health-related, developmental, and organizational concerns—such as improving well-being, alleviating distress and maladjustment, and resolving crises—and addresses issues from individual, family, group, systems, and organizational perspectives. The counseling psychologist has received professional education and training in one or more counseling areas, such as educational, vocational, employee, aging, personal, marriage, or rehabilitation counseling. In contrast to a clinical psychologist (see clinical psychology), who usually emphasizes origins of maladaptations, a counseling psychologist emphasizes adaptation, adjustment, and more efficient use of the individual’s available resources.' - APA

Couples Therapy

'therapy in which both partners in a committed relationship are treated at the same time by the same therapist or therapists. Couples therapy is concerned with problems within and between the individuals that affect the relationship. For example, one partner may have undiagnosed depression that is affecting the relationship, or both partners may have trouble communicating effectively with one another. Individual sessions may be provided separately to each partner, particularly at the beginning of therapy; most of the course of therapy, however, is provided to both partners together. Couples therapy for married couples is known as marital therapy.' - APA

Cerebrospinal Fluid (CSF)

'the fluid within the central canal of the spinal cord, the four ventricles of the brain, and the subarachnoid space of the brain. It serves as a watery cushion to protect vital tissues of the central nervous system from damage by shock pressure, and it mediates between blood vessels and brain tissue in exchange of materials, including nutrients.' -APA

Cell Body

'the part of a neuron (nerve cell) that contains the nucleus and most organelles. Also called perikaryon; soma.' - APA

Cerebral Hemisphere

'either half (left or right) of the cerebrum. The hemispheres are separated by a deep longitudinal fissure, but they are connected by commissural, projection, and association fibers so that each side of the brain normally is linked to functions of tissues on either side of the body. See also hemispheric lateralization.' - APA

Clinical Psychology

'the branch of psychology that specializes in the research, assessment, diagnosis, evaluation, prevention, and treatment of emotional and behavioral disorders. Clinical psychologists are doctorate-level professionals who have received training in research methods and techniques for the diagnosis and treatment of various psychological disorders. They work primarily in health and mental health clinics, in research, in academic settings, or in group and independent practices. They also serve as consultants to other professionals in the medical, legal, social-work, and community-relations fields. Clinical psychologists comprise approximately one third of the psychologists working in the United States and are governed by the code of practice of the American Psychological Association and by state licensing requirements.' - APA


'the largest part of the brain, forming most of the forebrain and lying in front of and above the cerebellum. It consists of two cerebral hemispheres bridged by the corpus callosum. Each hemisphere is divided into four main lobes: the frontal lobe, occipital lobe, parietal lobe, and temporal lobe. The outer layer of the cerebrum—the cerebral cortex—is intricately folded and composed of gray matter. Also called telencephalon. [Latin, literally: “brain”]' - APA

Cognitive Therapy (CT)

'a form of psychotherapy based on the concept that emotional and behavioral problems in an individual are, at least in part, the result of maladaptive or faulty ways of thinking and distorted attitudes toward oneself and others. The objective of the therapy is to identify these faulty cognitions and replace them with more adaptive ones, a process known as cognitive restructuring. The therapist takes the role of an active guide who attempts to make the client aware of these distorted thinking patterns and who helps the client correct and revise his or her perceptions and attitudes by citing evidence to the contrary or by eliciting it from the client. See also cognitive behavior therapy. Also called Beck therapy. [developed by Aaron T. Beck]' - APA

Central Canal

'the channel in the center of the spinal cord, which contains cerebrospinal fluid.' - APA

Central Nervous System (CNS)

'the entire complex of neurons, axons, and supporting tissue that constitute the brain and spinal cord. The CNS is primarily involved in mental activities and in coordinating and integrating incoming sensory messages and outgoing motor messages. Compare peripheral nervous system.' - APA


(pl. Cerebella)

'a portion of the hindbrain dorsal to the rest of the brainstem, to which it is connected by the cerebellar peduncles. The cerebellum modulates muscular contractions to produce smooth, accurately timed ballistic movements; it helps maintain equilibrium by predicting body positions ahead of actual body movements, and it is required for some kinds of motor conditioning. [Latin, literally: “little brain,” diminutive of cerebrum]' - APA

Cerebral Cortex

'the layer of gray matter that covers the outside of the cerebral hemispheres in the brain and is associated with higher cognitive functions, such as language, learning, perception, and planning. It consists mostly of neocortex, which has six main layers of cells; regions of cerebral cortex that do not have six layers are known as allocortex. Differences in the cytoarchitecture of the layers led to the recognition of distinct areas, called Brodmann’s areas, many of which are known to serve different functions.' - APA

Corticomedial Group

'one of the two main groups of nuclei in the amygdala within the brain. It includes the central nucleus and receives mainly olfactory and pheromonal information; its output, via the stria terminalis, is to the hypothalamus and the basomedial forebrain. See also basolateral group.' - APA

Client-Centered Therapy

'a form of psychotherapy developed by Carl Rogers in the early 1940s. According to Rogers, an orderly process of client self-discovery and actualization occurs in response to the therapist’s consistent empathic understanding of, acceptance of, and respect for the client’s frame. The therapist sets the stage for personality growth by reflecting and clarifying the ideas of the client, who is able to see himself or herself more clearly and come into closer touch with his or her real self. As therapy progresses, the client resolves conflicts, reorganizes values and approaches to life, and learns how to interpret his or her thoughts and feelings, consequently changing behavior that he or she considers problematic. It was originally known as nondirective counseling or nondirective therapy, although this term is now used more broadly to denote any approach to psychotherapy in which the therapist establishes an encouraging atmosphere but avoids giving advice, offering interpretations, or engaging in other actions to actively direct the therapeutic process. Also called client-centered psychotherapy; person-centered therapy; Rogerian therapy.' - APA

Corpus Callosum

'a large tract of nerve fibers running across the longitudinal fissure of the brain and connecting the cerebral hemispheres: It is the principal connection between the two sides of the brain. The largest of the interhemispheric commissures, it is known as the great commissure. ' - APA

Cervical Nerve

'any of the eight spinal nerves in the neck area. Each has a dorsal root that is sensory in function and a ventral root that has motor function.' - APA

Commissural Fiber

'an axon from any of various neurons that connect the same or equivalent structures in the left and right cerebral hemispheres.' - APA

Correctional Psychology

'a branch of forensic psychology concerned with the application of counseling and clinical techniques to criminal and juvenile offenders in penal and correctional facilities (e.g., reformatories, penitentiaries). Correctional psychologists also participate professionally in court activities, probation departments, parole boards, prison administration, supervision of inmate behavior, and programs for the rehabilitation of offenders.' - APA

Conjoint Therapy

'therapy in which the partners in a relationship or members of a family are treated together in joint sessions by one or more therapists, instead of being treated separately. Also called conjoint counseling. ' - APA

Cognitive Behaviour Therapy (CBT)

'a form of psychotherapy that integrates theories of cognition and learning with treatment techniques derived from cognitive therapy and behavior therapy. CBT assumes that cognitive, emotional, and behavioral variables are functionally interrelated. Treatment is aimed at identifying and modifying the client’s maladaptive thought processes and problematic behaviors through cognitive restructuring and behavioral techniques to achieve change. Also called cognitive behavior modification; cognitive behavioral therapy' - APA

Cognitive Analytic Therapy

'a time-limited, collaborative psychotherapy that emphasizes schemas and integrates principles and techniques from psychodynamic psychotherapy and cognitive behavior therapy. [developed in the 1980s by British psychiatrist Anthony Ryle (1927–  )]' - APA


'the largest part of the brain, forming most of the forebrain and lying in front of and above the cerebellum. It consists of two cerebral hemispheres bridged by the corpus callosum. Each hemisphere is divided into four main lobes: the frontal lobe, occipital lobe, parietal lobe, and temporal lobe. The outer layer of the cerebrum—the cerebral cortex—is intricately folded and composed of gray matter. Also called telencephalon. [Latin, literally: “brain”]' - APA

Compulsive Disorder

'any disorder in which the individual feels forced to perform acts that are against his or her wishes or better judgment. The act may be associated with an experience of pleasure or gratification (e.g., compulsive gambling, drinking, or drug taking) or with the reduction of anxiety or distress (e.g., rituals in obsessive-compulsive disorder). See intermittent explosive disorder; kleptomania; paraphilia; pathological gambling; pyromania; substance abuse; trichotillomania. ' - APA

Dance Thearpy

'the use of various forms of rhythmic movement—classical, modern, folk, or ballroom dancing; exercises to music; and the like—as a therapeutic technique to help individuals achieve greater body awareness and social interaction and enhance their psychological and physical functioning. See also movement therapy. [pioneered in 1942 by U.S. dance professional Marian Chace (1896–1970)]' - APA


'a generalized, pervasive deterioration of memory and at least one other cognitive function, such as language and an executive function, due to a variety of causes. The loss of intellectual abilities is severe enough to interfere with an individual’s daily functioning and social and occupational activity. In DSM–IV–TR, dementias are categorized according to the cause, which may be Alzheimer’s disease, cerebrovascular disease, Lewy body dementia, Pick’s disease, Parkinson’s disease, Huntington’s disease, HIV infection, Creutzfeldt–Jakob disease, head injury, alcoholism , or substance abuse. Brain tumor, hypothyroidism, hematoma, or other conditions, which may be treatable, can also cause dementia. The age of onset varies with the cause but is usually late in life. When occurring after the age of 65, it is termed senile dementia, and when appearing before 65, it is called presenile dementia, although these distinctions are becoming obsolete because its manifestations are the same no matter the age of onset. Dementia should not be confused with age-associated memory impairment or mild cognitive impairment, which have a much less deleterious effect on day-to-day functioning. DSM–5 has subsumed dementia and amnestic disorder into the diagnostic category major neurocognitive disorder, although it still accepts the term dementia where commonly used.' - APA


'denoting the hind region or the back surface of the body. In reference to the latter, this term sometimes is used interchangeably with posterior.' 

Dura Matter

'the outermost and strongest of the three layers of membranes (meninges) that cover the brain and spinal cord.' - APA

Drama Therapy

'in group therapy, the use of theater techniques to gain self-awareness and increase self-expression.' - APA

Dopamine (DA)

'a catecholamine neurotransmitter that has an important role in motor behavior and is implicated in numerous mental conditions and emotional states. It is found in dopaminergic neurons in the brain and elsewhere. It is synthesized from the dietary amino acid tyrosine, which in the first, rate-limiting stage of the reaction is converted to L-dopa (3,4-dihydroxylphenylalanine; see levodopa) by the enzyme tyrosine hydroxylase. L-dopa is then transformed into dopamine by the enzyme dopa decarboxylase. In nondopaminergic neurons and the adrenal medulla, dopamine is further metabolized to form norepinephrine and epinephrine, respectively. Destruction of the dopaminergic neurons in the substantia nigra is responsible for the symptoms of Parkinson’s disease (e.g., rigidity, tremor). Blockade of the actions of dopamine in other brain regions accounts for the therapeutic activities of many anypsychotic drugs.' -APA

Depressive Disorder

'in DSM–IV–TR and DSM–5, any of the mood disorders that typically have sadness as the predominant symptom. They primarily include major depressive disorder and dysthymic disorder.' - APA

Dura Matter

'the outermost and strongest of the three layers of membranes (meninges) that cover the brain and spinal cord.' - APA


'a branching, threadlike extension of the cell body that increases the receptive surface of a neuron. The full arrangement of the dendrites of a single neuron is termed a dendritic tree, and the specific pattern and quality of that arrangement is termed dendritic branching.' - APA


'1.a negative affective state, ranging from unhappiness and discontent to an extreme feeling of sadness, pessimism, and despondency, that interferes with daily life. Various physical, cognitive, and social changes also tend to co-occur, including altered eating or sleeping habits, lack of energy or motivation, difficulty concentrating or making decisions, and withdrawal from social activities. It is symptomatic of a number of mental health disorders. psychiatry and psychology, any of the depressive disorders. ' - APA


'a neurologically based learning disability manifested as severe difficulties in reading, spelling, and writing words and sometimes in arithmetic. Dyslexia is characterized by impairment in the ability to process sounds, that is, to make connections between written letters and their sounds; written work is often characterized by reversal errors. It can be either acquired (in which case it is often referred to as alexia) or developmental (see developmental dyslexia), is independent of intellectual ability, and is unrelated to disorders of speech and vision that may also be present. It is not the result of lack of motivation, sensory impairment, inadequate instructional or environmental opportunities, emotional disturbances, or other such factors. Since the 1960s, information-processing and other psychological accounts of acquired dyslexia have prompted investigators to subdivide it into two general classes: (a) visual word-form dyslexia, which is characterized by difficulty in the visual analysis of written words; and (b) central dyslexia, which is characterized by difficulty in later stages of the reading process (i.e., pronunciation and comprehension). Various types and subtypes of dyslexia, both acquired and developmental, have also been proposed, but there is no universally accepted system of classification. See also reading disability; reading disorder.' - APA


'a reduction in the electric potential across the plasma membrane of a cell, especially a neuron, such that the inner surface of the membrane becomes less negative in relation to the outer surface. Depolarization occurs when the membrane is stimulated and sodium ions (Na+) flow into the cell. If the stimulus intensity exceeds the excitatory threshold of the neuron, an action potential is created and a nerve impulse propagated.' - APA

Dyshymic Disorder

'in DSM–IV–TR, a mood disorder characterized by symptoms that are less severe but more enduring than those in major depressive disorder. It is identified as persistent depressive disorder in DSM–5. Also called dysthymia.' - APA

Delusional Disorder

'in DSM–IV–TR, any one of a group of psychotic disorders with the essential feature of one or more nonbizarre delusions that persist for at least 1 month but are not due to schizophrenia. The delusions are nonbizarre in that they feature situations that could conceivably occur in real life (e.g., being followed, poisoned, infected, deceived by one’s government). Diagnosis also requires that the effects of substances (e.g., cocaine) or a medical condition be ruled out as causes of the delusions. Seven types of delusional disorder are specified, according to the theme of the delusion: erotomanic, grandiose, jealous, persecutory, somatic, mixed, and unspecified. Criteria changes for delusional disorder in DSM–5 include the following: The delusions may be either nonbizarre or bizarre (i.e., implausible), and their potential presence as a result of an ingested substance, a medical condition, or another mental disorder sometimes associated with firmly held delusional beliefs (e.g., obsessive-compulsive disorder, body dysmorphic disorder) must be ruled out. Formerly called paranoid disorder.' - APA

Educational Psychology

'a branch of psychology dealing with the application of psychological principles and theories to a broad spectrum of teaching, training, and learning issues in educational settings. Educational psychology also addresses psychological problems that can arise in educational systems. Educational psychologists often hold applied as well as academic positions, spending their time in a variety of teaching, research, and applied pursuits.' - APA

Experiential Psychotherapy

'a broad family of psychotherapies originating in the 1950s and 1960s and falling under the umbrella of existential–humanistic psychology. A core belief of the approach is that true client change occurs through direct, active “experiencing” of what the client is undergoing and feeling at any given point in therapy, both on the surface and at a deeper level. Experiential therapists typically engage clients very directly with regard to accessing and expressing their inner feelings and experiencing both present and past life scenes, and they offer clients perspectives for integrating such experiences into realistic and healthy self-concepts. Experiential psychotherapy has its antecedents in the work of U.S. psychiatrists Carl A. Whitaker (1912–1995) and Thomas P. Malone (d. 2000), Austrian-born U.S. psychologist Carl Rogers, U.S. philosopher and psychologist Eugene T. Gendlin (1926–  ), and others.' - APA

Ependymal Cell

'a type of nonneuronal central nervous system cell (glia) that comprises the ependyma and helps circulate cerebrospinal fluid.' - APA

Experimental Psychology

'the scientific study of behavior, motives, or cognition in a laboratory or other controlled setting in order to predict, explain, or influence behavior or other psychological phenomena. Experimental psychology aims at establishing quantified relationships and explanatory theory through the analysis of responses under various controlled conditions and the synthesis of adequate theoretical accounts from the results of these observations.' - APA

Entorhinal Cortex

'a region of cerebral cortex in the ventromedial portion of the temporal lobe. It has reciprocal connections with the hippocampal formation and various other cortical and subcortical structures and is an integral component of the medial temporal lobe memory system. It is also involved in spatial navigation. Lesions in this area are used to study neural plasticity and working memory; they are also seen in temporal lobe epilepsy and the early stages of Alzheimer’s disease.' - APA

Empirical Psychology

'an approach to the study and explanation of psychological phenomena that emphasizes objective observation' - APA

Endocrine Gland

'any ductless gland that secretes hormones directly into the bloodstream to act on distant targets. Such glands include the pituitary gland, adrenal gland, thyroid gland, gonads (testis and ovary), and islets of Langerhans. Together, they comprise the endocrine system. ' - APA

Existential Psychotherapy

'a form of psychotherapy that deals with the here and now of the client’s total situation rather than with his or her past or underlying dynamics. It emphasizes the exploration and development of meaning in life, focuses on emotional experiences and decision making, and stresses a person’s responsibility for his or her own existence.' - APA

Executive Functions

'higher level cognitive processes of planning, decision making, problem solving, action sequencing, task assignment and organization, effortful and persistent goal pursuit, inhibition of competing impulses, flexibility in goal selection, and goal-conflict resolution. These often involve the use of language, judgment, abstraction and concept formation, and logic and reasoning. They are frequently associated with neural networks that include the frontal lobe, particularly the prefrontal cortex. Deficits in executive functioning are seen in various disorders, including Alzheimer’s disease and schizophrenia. In the latter, for example, selection and maintenance of goals may be impaired, as may the ability to exclude distractions. Also called central processes; higher order processes.' - APA

Frontal Cortex

'the cerebral cortex of the frontal lobe. It is associated with decision making, planning, insight, judgment, the ability to concentrate, and impulse control.' - APA

Frontal Lobe

'one of the four main lobes of each cerebral hemisphere of the brain, lying in front of the central sulcus. It is concerned with motor and higher order executive functions. ' - APA

Family Therapy

'a form of psychotherapy that focuses on the improvement of interfamilial relationships and behavioral patterns of the family unit as a whole, as well as among individual members and groupings, or subsystems, within the family. Family therapy includes a large number of treatment forms with diverse conceptual principles, processes and structures, and clinical foci. Some family therapy approaches (e.g., object relations theory) reflect extensions of models of psychotherapy with individuals in the interpersonal realm, whereas others (e.g., structural family therapy) evolved in less traditional contexts. Most approaches emphasize contexts in which clinical problems arise. This accompanying systemic view potentially allows clinical attention to all levels of the organization of behavior, from the individual, to the family, and to the community. Family therapy models vary enormously in terms of length, past versus present orientation, techniques used, and treatment goals. See also conjoint therapy; couples therapy; family group psychotherapy; family systems theory.' - APA

Forensic Psychology

'the application of psychological principles and techniques to situations involving the civil and criminal legal systems. Its functions include assessment and treatment services, provision of advocacy and expert testimony, policy analysis, and research on such topics as eyewitness accounts, offender behavior, interrogations, and investigative practices. Also called legal psychology.' - APA


'the part of the brain that develops from the anterior section of the neural tube in the embryo, containing the cerebrum and the diencephalon. The former comprises the cerebral hemispheres with their various regions (e.g., basal ganglia, amygdala, hippocampus); the latter comprises the thalamus and hypothalamus. Also called prosencephalon.' - APA 


'a ridged or raised portion of the cerebral cortex, bounded on either side by a sulcus.' - APA


(pl. Ganglia)

'a collection of cell bodies of neurons that lies outside the central nervous system (the basal ganglia, however, are an exception). Many invertebrates have only distributed ganglia and no centralized nervous system. ' - APA


'an amino acid that serves as one of the two major inhibitory neurotransmitters in the central nervous system (particularly the spinal cord), the other being gamma-aminobutyric acid (GABA). Glycine is also a cotransmitter with glutamate at excitatory NMDA receptors. Glycine synthesis occurs via two different pathways; in the most important of these, glycine is synthesized from the amino acid serine in a single reaction catalyzed by the enzyme serine hydroxymethyltransferase.' - APA

Grey Matter

'any area of neural tissue that is dominated by cell bodies and is devoid of myelin, such as the cerebral cortex and the H-shaped periaqueductal gray of the spinal cord.' - APA


'nonneuronal tissue in the nervous system that provides structural, nutritional, and other kinds of support to neurons. It may consist of very small cells (microglia) or relatively large ones (macroglia). The latter include astrocytes, ependymal cells, and the two types of cells that form the myelin sheath around axons: oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system. Also called neuroglia.' -APA

Group Therapy

'treatment of psychological problems in which two or more participants interact with each other on both an emotional and a cognitive level in the presence of one or more psychotherapists who serve as catalysts, facilitators, or interpreters. The approaches vary, but in general they aim to provide an environment in which problems and concerns can be shared in an atmosphere of mutual respect and understanding. Group therapy seeks to enhance self-respect, deepen self-understanding, and improve interpersonal relationships. Also called group psychotherapy. ' - APA


'a salt or ester of the amino acid glutamic acid that serves as the predominant excitatory neurotransmitter in the brain. Glutamate plays a critical role in cognitive, motor, and sensory functions. It exerts its effects by binding to glutamate receptors on neurons. Excessive activity of glutamate at these receptors is associated with damage to nerve tissue (neurotoxicity) and cell death, possibly the result of calcium ions flooding into the cell following overstimulation of NMDA receptors.' - APA

Gestalt Therapy

'a form of psychotherapy in which the central focus is on the totality of the client’s functioning and relationships in the here and now rather than on investigation of past experiences and developmental history. One of the themes is that growth occurs by assimilation of what is needed from the environment and that psychopathology arises as a disturbance of contact with the environment. Gestalt techniques, which can be applied in either a group or an individual setting, are designed to bring out spontaneous feelings and self-awareness and promote personality growth. Examples of such techniques are role play, the empty-chair technique, and the hot-seat technique. [first proposed in the 1940s by German-born U.S. psychiatrist Frederick (Fritz) S. Perls (1893–1970)]' - APA


'abbreviation for gamma-aminobutyric acid. a major inhibitory neurotransmitter in the mammalian nervous system and found widely distributed in both invertebrate and vertebrate nervous systems. It is synthesized from the amino acid glutamic acid. See also GABAA receptorgabaa-receptor; GABAB receptorgabab-receptor.' - APA 

Health Psychology

'the subfield of psychology that focuses on (a) the examination of the relationships between behavioral, cognitive, psychophysiological, and social and environmental factors and the establishment, maintenance, and detriment of health; (b) the integration of psychological and biological research findings in the design of empirically based interventions for the prevention and treatment of illness; and (c) the evaluation of physical and psychological status before, during, and after medical and psychological treatment. Also called health care psychology.' - APA

Hippocampal Formation

'a region of the brain located in the medial temporal lobe and concerned with the consolidation of long-term memory. It comprises the dentate gyrus, hippocampus, and subiculum and communicates with areas of neocortex via the entorhinal cortex.' - APA


'the posterior of three bulges that appear in the embryonic brain as it develops from the neural tube. The bulge eventually becomes the medulla oblongata, pons, and cerebellum.' - APA

Human Factors Psychology

'a branch of psychology that studies the role of human factors in operating systems, with the aim of redesigning environments, equipment, and processes to fit human abilities and characteristics.' - APA


'a seahorse-shaped part of the forebrain, in the basal medial region of the temporal lobe, that is important for declarative memory and learning. Because of its resemblance to a ram’s horn, 19th-century neuroanatomists named it Ammon’s horn (cornu ammonis; CA) for the horn of the ram that represented the Egyptian deity Ammon. Parts of the hippocampus were then labeled CA1, CA2, CA3, and CA4; these designations are still used for the different regions of the hippocampus.' - APA

Humanistic Therapy

'any of a variety of psychotherapeutic approaches that reject psychoanalytic and behavioral approaches; seek to foster personal growth through direct experience; and focus on the development of human potential, the here and now, concrete personality change, responsibility for oneself, and trust in natural processes and spontaneous feeling. Some examples of humanistic therapy are client-centered therapy, gestalt therapy, existential psychotherapy, and experiential psychotherapy.' - APA


'an increase in the electric potential across the plasma membrane of a cell, especially a neuron, such that the inner surface of the membrane becomes more negative in relation to the outer surface. It occurs during the final portion of an action potential or in response to inhibitory neural messages.' - APA


'part of the diencephalon of the brain, lying ventral to the thalamus, that contains nuclei with primary control of the autonomic (involuntary) functions of the body. It also helps integrate autonomic activity into appropriate responses to internal and external stimuli. Additionally, it is involved in appetite, thirst, sleep, and sexuality.' - APA


'a substance secreted into the bloodstream by an endocrine gland or other tissue or organ to regulate processes in distant target organs and tissues. These secretions include those from the anterior and posterior pituitary gland; the corticosteroids and epinephrine, secreted by the adrenal glands; and the sex hormones released by the reproductive glands. Other organs that secrete hormones include the hypothalamus and the stomach, which emits at least five: cholecystokinin, enterogastrone, gastrin, ghrelin, and secretin.'

Individual Therapy

'treatment of psychological problems that is conducted on a one-to-one basis. One therapist sees one client at a time, tailoring the process to his or her unique needs in the exploration of contributory factors and alleviation of symptoms. Also called dyadic therapy; individual psychotherapy. ' - APA

Integrative Psychotherapy

'psychotherapy that selects theoretical models or techniques from various therapeutic schools to suit the client’s particular problems. For example, psychodynamic psychotherapy and gestalt therapy may be combined through the practice of interpretation of material in the here and now. The Society for the Exploration of Psychotherapy Integration (SEPI), founded in 1983, reflects the growing interest in, and the rapid development and use of, such combined therapeutic techniques. Also called psychotherapy integration. See also eclectic psychotherapy.' - APA

Inferior Colliculus

'either of the caudal pair of colliculi. They receive and process auditory nerve impulses and relay these to the medial geniculate nuclei.' - APA


'any neuron that is neither sensory nor motor but connects other neurons within the central nervous system. Also called connector neuron.' - APA






'an approach to psychotherapy that focuses on the “human predicament,” helping the client to overcome crises in meaning. The therapeutic process typically consists of examining three types of values: (a) creative (e.g., work, achievement), (b) experiential (e.g., art, science, philosophy, understanding, loving), and (c) attitudinal (e.g., facing pain and suffering). Each client is encouraged to arrive at his or her own solution, which should incorporate social responsibility and constructive relationships. Also called meaning-centered therapy. See also existential psychotherapy; existentialism. [developed in the 1950s and 1960s by Viktor E. Frankl]' - APA

Limbic System

'a loosely defined, widespread group of brain nuclei that innervate each other to form a network that is involved in autonomic and visceral processes and mechanisms of emotion, memory, and learning. It includes portions of the cerebral cortex (see limbic lobe), thalamus, and certain cortical and subcortical structures, such as the hippocampus, amygdala, and septal area.' - APA

Limbic Lobe

'a fifth subdivision of each cerebral hemisphere that is often distinguished in addition to the four main lobes. It comprises the cingulate cortex, parahippocampal gyrus, and hippocampal formation.' - APA

Medial Temporal Lobe

'the region toward the middle of the temporal lobe of each cerebral hemisphere. It contains the pyriform area, the amygdala, and the hippocampus. It is involved particularly in learning and memory.' - APA

Medulla Oblongata

'the most inferior (lowest), or caudal (tailward), part of the hindbrain. It contains many nerve tracts that conduct impulses between the spinal cord and higher brain centers, as well as autonomic nuclei involved in the control of breathing, heartbeat, and blood pressure. Also called myelencephalon.' - APA

Multipolar Neuron

'a neuron that has many dendrites and a single axon extending from the cell body. Also called multipolar cell.' - APA

Major Depressive Diorder

'in DSM–IV–TR and DSM–5, a mood disorder characterized by persistent sadness and other symptoms of a major depressive episode but without accompanying episodes of mania or hypomania or mixed episodes of depressive and manic or hypomanic symptoms. Also called major depression.' - APA

Music Therapy

'the use of music as an adjunct to the treatment or rehabilitation of individuals to enhance their psychological, physical, cognitive, or social functioning. Music therapy involves singing, writing music, performing music, listening to music, and lyric analysis, among other techniques.' - APA


'a relatively small region of the upper brainstem that connects the forebrain and hindbrain. It contains the tectum (and associated inferior and superior colliculi), tegmentum, and substantia nigra. Also called mesencephalon.' - APA

Multipolar Neuron

'a neuron that has many dendrites and a single axon extending from the cell body. Also called multipolar cell.' - APA

Mood Disorder

'in DSM–IV–TR, a psychiatric condition in which the principal feature is a prolonged, pervasive emotional disturbance, such as a depressive disorder, bipolar disorder, or substance-induced mood disorder. Also included are mood disorders due to a general medical condition, in which attendant physiological disruptions are believed to produce the emotional changes, and mood disorder not otherwise specified, which does not meet the diagnostic criteria for any of the specific mood disorders. The term chronic mood disorder is applied when symptoms rarely remit. In DSM–5, mood disorders are divided into two categories: bipolar and related disorders, which include bipolar disorder and its subtypes (e.g., bipolar I, bipolar II, cyclothymic disorder); and depressive disorders (e.g., major depressive disorder, persistent depressive disorder or dysthymic disorder, premenstrual dysphoric disorder). Also called affective disorder.' - APA

Motor Cortex

'the region of the frontal lobe of the brain responsible for the control of voluntary movement. It is divided into two parts. The primary motor cortex, or motor area, is the main source of neurons in the corticospinal tract. The secondary (or nonprimary) motor cortex, made up of the premotor area and the supplementary motor area, is specialized for planning upcoming movements and learning new movements. Lesions in the primary motor cortex due to stroke or traumatic injury usually cause initial paralysis that may improve to a condition involving weakness and poor muscle tone. Lesions in the secondary motor cortex usually cause disruptions in motor planning for complex movements (see apraxia). Also called motor strip.' - APA

Myelin Sheath

'the insulating layer around many axons that increases the speed of conduction of nerve impulses. It consists of myelin and is laid down by glia, which wrap themselves around adjacent axons. The myelin sheath is interrupted by small gaps, called nodes of Ranvier, which are spaced about every millimeter along the axon. Also called medullary sheath.' - APA

Membrane Potential

'a difference in electric potential across a membrane, especially the plasma membrane of a cell. At rest, the membrane potential intracellularly is usually negative; that is, the inside of a cell membrane is comparatively negative versus the outside.' - APA

Mental Disorder

'any condition characterized by cognitive and emotional disturbances, abnormal behaviors, impaired functioning, or any combination of these. Such disorders cannot be accounted for solely by environmental circumstances and may involve physiological, genetic, chemical, social, and other factors. Specific classifications of mental disorders are elaborated in the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (see DSM–IV–TR; DSM–5) and the World Health Organization’s International Classification of Diseases. Also called mental illness; psychiatric disorder; psychiatric illness; psychological disorder.' - APA


'the three membranous layers that provide a protective cover for the brain and spinal cord. They consist of a tough outer dura mater, a middle arachnoid mater, and a thin, transparent pia mater, which fits over the various contours and fissures of the cerebral cortex.' - APA


'an amine that contains only one amine group, –NH2. Monoamines include neurotransmitters such as the catecholamines norepinephrine and dopamine and the indoleamine serotonin. See also monoamine oxidase.' -APA


'an amine hormone, produced mainly by the pineal gland as a metabolic product of the neurotransmitter serotonin, that helps to regulate seasonal changes in physiology and may also influence puberty. It is implicated in the initiation of sleep and in the regulation of the sleep–wake cycle. Melatonin has been investigated in clinical studies as a hypnotic and for the management of circadian rhythm sleep disorders. Although these studies are as yet inconclusive, melatonin is widely available as an over-the-counter medication.' - APA


' the basic cellular unit of the nervous system. Each neuron is composed of a cell body; fine, branching extensions (dendrites) that receive incoming nerve signals; and a single, long extension (axon) that conducts nerve impulses to its branching terminal. The axon terminal transmits impulses to other neurons or to effector organs (e.g., muscles and glands) via junctions called synapses or neuromuscular junctions. Neurons can be classified according to their function as motor neurons, sensory neurons, or interneurons. There are various structural types, including unipolar neurons, bipolar neurons, and multipolar neurons. The axons of vertebrate neurons are often surrounded by a myelin sheath. In contrast to other cell types, neurons possess the capacity to modify their structure and function based on the receipt of information and stimuli from their immediate environnent (see neural plasticity). Also called nerve cell. [term coined by German physician Heinrich Wilhelm von Waldeyer-Hartz (1836–1921)]' - APA


'a weblike network of axon and dendrite filaments that forms the bulk of the gray matter of the central nervous system. The cell bodies of neurons are embedded in the network of fibers.' - APA 


'a substance that modulates the effectiveness of a neurotransmitter by influencing its release or receptor response to it. ' - APA


(pl. Nuclei)

' 1. a large membrane-bound compartment, found in the cells of nonbacterial organisms, that contains the bulk of the cell’s genetic material in the form of chromosomes.

2. in the central nervous system, a mass of cell bodies belonging to neurons with the same or related functions. Examples are the amygdaloid nuclei, the basal nuclei, the thalamic nuclei, and the nucleus accumbens.' - APA


'a catecholamine neurotransmitter and hormone produced mainly by brainstem nuclei and in the adrenal medulla. Also called norepinephrine' - APA

Node of Ranvier

'any of successive regularly spaced gaps in the myelin sheath surrounding an axon. The gaps permit the exchange of ions across the plasma membrane at those points, allowing the nerve impulse to leap from one node to the next in so-called saltatory conduction along the axon. [Louis A. Ranvier (1835–1922), French pathologist]' -APA 


'the branch of science that studies the physiological processes of the nervous system and relates them to behavior and cognition, in terms both of their normal function and of the dysfunctional processes associated with brain damage.' - APA


'any of a large number of chemicals that can be released by neurons to mediate transmission of nerve signals across the junctions (synapses) between neurons. When triggered by a nerve impulse, the neurotransmitter is released from the terminal button (see axon), travels across the synaptic cleft, and binds to and reacts with receptor molecules in the postsynaptic membrane. Neurotransmitters include amines (e.g., norepinephrine, serotonin) and amino acids (e.g., glutamate, glycine). Some neurotransmitters can be categorized as generally excitatory (e.g., glutamate, glysine) or generally inhibitory (e.g. gamma-aminobutyric acid). Excitatory neurotransmitters exert a facilitatory or activating downstream effect on postsynaptic neurons. That is, they depolarize the postsynaptic neurons, resulting in a greater likelihood of an action potential. Inhibitory neurotransmitters hyperpolarize the postsynaptic neurons—thereby making the intracellular space more negative, and hence, requiring a greater positive charge to overcome—resulting in a smaller likelihood of an action potential. However, some neurotransmitters have both excitatory and inhibitory receptors; these include acetylcholine and dopamine. Also called chemical transmitter; synaptic transmitter.' - APA


'any of several peptides that are released by neurons as neurotransmitters or neurohormones. They include the endogenous opioids (e.g., enkephalin, endorphin); peptides found in both the brain and the peripheral nervous system (e.g., substance P, neurotensin); hypothalamic releasing hormones (e.g., thyrotropin-releasing hormone); pituitary hormones (e.g., growth hormone, prolactin); and other circulating peptides (e.g., atrial natriuretic peptide, bradykinin).' - APA

Organizational Psychology

'the branch of psychology that studies human behavior in the work environment and applies general psychological principles to work-related issues and problems, notably in such areas as personnel selection, personnel training, employee evaluation, working conditions, accident prevention, job analysis, job satisfaction, leadership, team effectiveness, and work motivation. I/O psychologists conduct empirical research aimed at understanding individual and group behavior within organizations and use their findings to improve organizational effectiveness and the welfare of employees. Also called business psychology; employment psychology; industrial psychology; management psychology; occupational psychology; organizational psychology; work psychology.' - APA


'a type of nonneuronal central nervous system cell (glia) that forms myelin sheaths around axons. Also called oligodendrocyte' - APA

Orbitalfrontal Cortex

'the cerebral cortex of the ventral part of each frontal lobe, having strong connections to the hypothalamus. Lesions of the orbitofrontal cortex can result in loss of inhibitions, forgetfulness, and apathy broken by bouts of euphoria, as in the well-known case of Phineas Gage.' - APA

Occupational Health Psychology

'a specialty within psychology devoted to understanding workplace sources of health, illness, and injury and the application of this knowledge to improve the physical and mental well-being of employees.' - APA

Occipital Lobe

'the most posterior (rearward) subdivision of each cerebral hemisphere, roughly shaped like a pyramid and lying under the skull’s occipital bone. It contains several visual areas that receive and process visual stimuli, and it is involved in basic visual functions (e.g., visual acuity; contrast sensitivity; perception of color, form, and motion) as well as higher level ones (e.g., figure-ground segregation based on textural cues). A region of it, the occipital face area (OFA), has been identified as crucial to face recognition. See also fusiform gyrus.' - APA

Pre-frontal Cortex

'the most anterior (forward) part of the cerebral cortex of each frontal lobe in the brain. Divided into a dorsolateral region and an orbitofrontal region (see orbitofrontal cortex), the prefrontal cortex functions in attention, planning, working memory, and the expression of emotions and appropriate social behaviors; its development in humans parallels improvement in cognitive control and behavioral inhibition as an individual grows into adulthood. By contrast, damage to the prefrontal cortex leads to emotional, motor, and cognitive impairments. Also called frontal association area.' - APA

Peripheral Nervous System (PNS)

'the portion of the nervous system that lies outside the brain and spinal cord—that is, all parts outside the central nervous system. Afferent fibers of the PNS bring messages from the sense organs to the central nervous system; efferent fibers transmit messages from the central nervous system to the muscles and glands. The PNS includes the cranial nerves, spinal nerves, and parts of the autonomic nervous system.' - APA


'a part of the brainstem lying between the midbrain and the medulla oblongata, appearing as a swelling on the ventral surface of the brainstem. It consists of bundles of transverse, ascending, and descending nerve fibers and nuclei, including facial nerve nuclei. It serves primarily as a bridge, or transmission structure, between different areas of the nervous system. It also works with the cerebellum in controlling equilibrium and with the cerebral cortex in smoothing and coordinating voluntary movements. With the cerebellum, it forms the region called the metencephalon' - APA

Pyramidal Cell

'a type of large neuron that has a roughly pyramid-shaped cell body and is found in the cerebral cortex.' - APA

Personnel Psychology

'the branch of industrial and organizational psychology that deals with the selection, placement, training, promotion, evaluation, and counseling of employees.' -APA

Pia Matter

'a delicate membrane that covers the surface of the brain and spinal cord; it is the innermost layer of the three meninges. The cranial portion of the pia mater is richly supplied with blood vessels and closely follows the contours of the cerebral cortex, extending into the fissures and sulci.' -APA

Personality Disorder (PD)

'any in a group of disorders involving pervasive patterns of perceiving, relating to, and thinking about the environment and the self that interfere with long-term functioning of the individual and are not limited to isolated episodes. DSM–IV–TR recognizes 10 specific personality disorders organized within three clusters: Cluster A includes paranoid, schizoid, and schizotypal; Cluster B includes antisocial, borderline, histrionic, and narcissistic; and Cluster C includes avoidant, dependent, and obsessive-compulsive; each disorder has its own entry in the dictionary. These constructs emerged from different theoretical perspectives of the early 20th century. They do not, however, exhaust the list of possible clinically significant maladaptive personality traits, and many of the DSM–IV–TR disorders are themselves often difficult to diagnose reliably; indeed, research has shown that many people diagnosed with a PD qualify for more than one. Conversely, personality disorder not otherwise specified, a residual category included within the DSM–IV–TR classification, is a highly common PD diagnosis in clinical settings, applied to patients whom clinicians determine to have a personality disorder but who do not meet the diagnostic criteria for any of the 10 disorders within the classification. DSM–5 retains the same clusters of disorders, as well as the same diagnostic criteria for them, but includes, for “further study,” a new model for PD classification, proposing impaired personality functioning and pathological personality traits as the main criteria for identifying the presence of a personality disorder.' - APA


'1. the scientific study of mental disorders, including their theoretical underpinnings, etiology, progression, symptomatology, diagnosis, and treatment. This broad discipline draws on research from numerous areas, such as psychology, biochemistry, pharmacology, psychiatry, neurology, and endocrinology. The term in this sense is sometimes used synonymously with abnormal psychology.

2.  the behavioral or cognitive manifestations of such disorders. The term in this sense is sometimes considered synonymous with mental disorder itself.' - APA


'any psychological service provided by a trained professional that primarily uses forms of communication and interaction to assess, diagnose, and treat dysfunctional emotional reactions, ways of thinking, and behavior patterns. Psychotherapy may be provided to individuals, couples (see couples therapy), families (see family therapy), or members of a group (see group therapy). There are many types of psychotherapy, but generally they fall into four major categories: psychodynamic psychotherapy, cognitive therapy or behavior therapy, humanistic therapy, and integrative psychotherapy. The psychotherapist is an individual who has been professionally trained and licensed (in the United States by a state board) to treat mental, emotional, and behavioral disorders by psychological means. He or she may be a clinical psychologist, psychiatrist, counselor, social worker, or psychiatric nurse. Also called therapy; talk therapy. —psychotherapeutic' - APA


'in back of or toward the back. In reference to two-legged upright animals, this term sometimes is used interchangeably with dorsal to mean toward the back surface of the body. ' - APA

Psychotic Disorder

'any of a number of severe mental disorders, regardless of etiology, characterized by gross impairment in reality testing. The accuracy of perceptions and thoughts is incorrectly evaluated, and incorrect inferences are made about external reality, even in the face of contrary evidence. Specific symptoms indicative of psychotic disorders are delusions, hallucinations, and markedly disorganized speech, thought, or behavior; individuals may have little or no insight into their symptoms. Some examples of psychotic disorders are schizophrenia, schizophreniform disorder, schizoaffective disorder, delusional disorder, brief psychotic disorder, and psychotic disorders due to a substance or to a medical condition.' - APA

Projection Fiber

'a nerve fiber that carries impulses from the cerebral cortex to subcortical structures (e.g., the thalamus, hypothalamus, basal ganglia).' -APA

Psychodynamic Psychotherapy

'those forms of psychotherapy, falling within or deriving from the psychoanalytic tradition, that view individuals as reacting to unconscious forces (e.g., motivation, drive), that focus on processes of change and development, and that place a premium on self-understanding and making meaning of what is unconscious. Most psychodynamic therapies share certain features, such as emphasis on dealing with the unconscious in treatment and on analyzing transference. Also called dynamic psychotherapy.' - APA


'a short chain of amino acids linked by peptide bonds. Peptides are usually identified by the number of amino acids in the chain. For example, dipeptides have two amino acids, tripeptides three, tetrapeptides four, and so on.' - APA


''Posttraumatic Stress Disorder

in DSM–IV–TR, a disorder that may result when an individual lives through or witnesses an event in which he or she believes that there is a threat to life or physical integrity and safety and experiences fear, terror, or helplessness. The symptoms are characterized by (a) reexperiencing the trauma in painful recollections, flashbacks, or recurrent dreams or nightmares; (b) avoidance of activities or places that recall the traumatic event, as well as diminished responsiveness (emotional anesthesia or numbing), with disinterest in significant activities and with feelings of detachment and estrangement from others; and (c) chronic physiological arousal, leading to such symptoms as an exaggerated startle response, disturbed sleep, difficulty in concentrating or remembering, and guilt about surviving the trauma when others did not. Subtypes are chronic posttraumatic stress disorder and dela yed posttraumatic stress disorder. When the symptoms do not last longer than 4 weeks, a diagnosis of acute stress disorder is given instead. Changes in PTSD criteria from DSM–IV–TR to DSM–5 include the following: Exposure to the traumatic event may be secondhand if the event happens to a loved one or if there is repeated exposure to aversive details (e.g., as with first responders cleaning up after a disaster); the subjective criterion requiring that the person feel fear, terror, or helplessness has been eliminated; symptom clusters have been recategorized, with additional symptoms; and separate criteria have been developed for children age 6 years or younger.' - APA



Rehabilitation neuropsychology

'a specialty area that studies and treats cognitive, behavioral, emotional, and social disturbances in individuals following stroke, traumatic brain injury, spinal cord injury, and other conditions involving neurological damage. The goal of rehabilitation neuropsychologists is to optimize the health, independence, and quality of life of their clients by (a) evaluating their executive functions and other abilities through observation of their behavior and administration of assessment instruments (e.g., neuropsychological tests); (b) providing cognitive retraining and other clinical interventions to facilitate skill reacquisition or substitution; (c) training and educating other professionals involved in their clients’ treatment; (d) participating in the development of public policy and other programs to benefit their clients; and (e) advocating on behalf of their clients (e.g., with insurance providers). The field is cross-disciplinary in nature, having relevance to such areas as community psychology, clinical psychology, counseling psychology, family medicine, health psychology, neurology, and psychiatry.' - APA

School Psychology

'a field of psychology concerned with the psychoeducational problems and other issues arising in primary and secondary schools. The responsibilities of the school psychologist include involvement in overall curriculum planning, individualized curriculum assessment and planning, administration of psychoeducational tests, interviews with parents concerning their child’s progress and problems, pupil behavior problems, counseling of teachers and students, and research on systematic educational questions and issues.' -APA

Septal Area

'a region of the forebrain that contains the septal nuclei and the septum pellucidum, which separates the lateral ventricles. The septal nuclei, which include the nucleus accumbens, form an integral part of the limbic system; they contribute fibers to the medial forebrain bundle and have interconnections with the amygdala, hippocampus, and regions of the hypothalamus. Functionality of this area includes pleasure generation and anger suppression.' -APA

Schizophreniform Disorder

'in DSM–IV–TR and DSM–5, a disorder whose essential features are identical to those of schizophrenia except that the total duration is between 1 and 6 months (i.e., intermediate between brief psychotic disorder and schizophrenia) and social or occupational functioning need not be impaired. The diagnosis applies without qualification to an episode of between 1 and 6 months’ duration from which the individual has already recovered. The diagnosis is provisional when there is no certainty of recovery within the 6-month period. If the disturbance persists beyond 6 months, the diagnosis would be changed to schizophrenia.' - APA

Superior Colliculus

'either of a pair of rounded prominences (colliculi) in the brain, one of which lies near each cerebral peduncle, rostrally to the inferior colliculus and immediately beneath the pineal gland. The superior colliculus receives fibers from the optic tract and projects fibers to several stations, including the lateral geniculate nucleus and the reticular formation. The superior colliculus gives rise to the tectospinal tract and is involved in orienting movements of the head and eye toward external stimuli. ' - APA

Social Psychology

'as defined by Gordon W. Allport, the study of how an individual’s thoughts, feelings, and actions are affected by the actual, imagined, or symbolically represented presence of other people. Psychological social psychology differs from sociological social psychology in that the former tends to put greater emphasis on internal psychological processes, whereas the latter focuses on factors that affect social life, such as status, role, and class.' -APA

Spinal Cord

'the part of the central nervous system that extends from the lower end of the medulla oblongata, at the base of the brain, through a canal in the center of the spine as far as the lumbar region. In transverse section, the cord consists of an H-shaped core of gray matter surrounded by white matter consisting of tracts of long ascending and descending nerve fibers on either side of the cord that are linked by the white commissure. The spinal cord is enveloped by the meninges and is the origin of the 31 pairs of spinal nerves.' - APA


'a common monoamine neurotransmitter in the brain, particularly the raphe nucleus, and in other parts of the central nervous system; it also is found in the gastrointestinal tract, in smooth muscles of the cardiovascular and bronchial systems, and in blood platelets. It is synthesized from the dietary amino acid L-tryptophan (see tryptophan hydroxylase), and in the pineal gland it is converted to melatonin. It is primarily degraded by monoamine oxidase, which yields its principal metabolic product, 5-hydroxyindoleacetic acid (5-HIAA). Serotonin has roles in emotional processing, mood, appetite, sexual desire and performance, sleep, pain processing, hallucinations, and reflex regulation. For example, levels of serotonin correlate negatively with aggression, and release of serotonin may promote sleep. It is implicated in many psychological conditions, including depressive disorders, anxiety disorders, sleep disorders, aggression, and psychosis; many common psychotropic drugs affect neurotransmission mediated by serotonin. Also called 5-hydroxytryptamine (5-HT).' - APA

Schwann Cell

'a type of nonneuronal peripheral nervous system cell (glia) that forms the myelin sheath around axons. Extensions of a single Schwann cell wind tightly and many times around several neighboring axons, so that the myelin sheath consists of multiple layers of the Schwann-cell plasma membrane. [Theodor Schwann (1810–1882), German physiologist]' - APA


'a groove, especially one on the surface of the cerebral cortex. The term is often used synonymously with fissure.' - APA


'the specialized junction through which neural signals are transmitted from one neuron (the presynaptic neuron) to another (the postsynaptic neuron). In most synapses, the knoblike ending (terminal button) of the axon of a presynaptic neuron faces the dendrite or cell body of the postsynaptic neuron across a narrow gap, the synaptic cleft. The arrival of a neural signal triggers the release of neurotransmitter from synaptic vesicles in the terminal button into the synaptic cleft. Here the molecules of neurotransmitter activate receptors in the postsynaptic membrane and cause the opening of ion channels in the postsynaptic cell. This may lead to excitation or inhibition of the postsynaptic cell, depending on which ion channels are affected. Also called synaptic junction. ' APA


'a psychotic disorder characterized by disturbances in thinking (cognition), emotional responsiveness, and behavior, with an age of onset typically between the late teens and mid-30s. Schizophrenia was first formally described in the late 19th century by Emil Kraepelin, who named it dementia praecox; in 1908, Eugen Bleuler renamed the disorder schizophrenia (Greek, “splitting of the mind”) to characterize the disintegration of mental functions associated with what he regarded as its fundamental symptoms of abnormal thinking and affect. According to DSM–IV–TR, the characteristic disturbances must last for at least 6 months and include at least 1 month of active-phase symptoms comprising two or more of the following: delusions, hallucinations, disorganized speech, grossly disorganized or catatonic behavior, or negative symptoms (e.g., lack of emotional responsiveness, extreme apathy). These signs and symptoms are associated with marked social or occupational dysfunction. Some have argued (beginning with Bleuler) that disorganized thinking (see formal thought disorder; schizophrenic thinking) is the single most important feature of schizophrenia, but DSM–IV–TR and its predecessors have not emphasized this feature, at least in their formal criteria. DSM–5 retains essentially the same criteria but emphasizes that delusions, hallucinations, or disorganized speech must be among the symptoms required for diagnosis. It also eliminates the five distinct subtypes of schizophrenia previously described in DSM–IV–TR: catatonic schizophrenia, disorganized schizophrenia, paranoid schizophrenia, residual schizophrenia, and undifferentiated schizophrenia.' - APA


'a region of the forebrain adjacent to the hippocampus that has reciprocal connections with the hippocampus and the dentate gyrus. It forms part of the hippocampal formation. Also called hippocampal gyrus.' - APA

Spinal Nerve

'any of the 31 pairs of nerves that originate in the gray matter of the spinal cord and emerge through openings between the vertebrae of the spine to extend into the body’s dermatomes (skin areas) and skeletal muscles. The spinal nerves comprise 8 cervical nerves, 12 thoracic nerves, 5 lumbar nerves, 5 sacral nerves, and 1 coccygeal nerve. Each attaches to the spinal cord via two short branches, a dorsal root and a ventral root. ' -APA

Spinal Nerve

'any of the 31 pairs of nerves that originate in the gray matter of the spinal cord and emerge through openings between the vertebrae of the spine to extend into the body’s dermatomes (skin areas) and skeletal muscles. The spinal nerves comprise 8 cervical nerves, 12 thoracic nerves, 5 lumbar nerves, 5 sacral nerves, and 1 coccygeal nerve. Each attaches to the spinal cord via two short branches, a dorsal root and a ventral root. ' -APA

Temporal Lobe

'one of the four main subdivisions of each cerebral hemisphere in the brain, lying immediately below the lateral sulcus on the outer surface of each hemisphere. It contains the auditory projection and auditory association areas and also areas for higher order visual processing. The medial temporal lobe contains regions important for memory formation.' - APA


'the central core of the midbrain and pons. It contains sensory and motor tracts passing through the midbrain and also several nuclei, including the oculomotor nucleus, red nucleus, and subthalamic nucleus.' - APA


'a mass of gray matter, forming part of the diencephalon of the brain, whose two lobes form the walls of the third ventricle. It consists of a collection of sensory, motor, autonomic, and associational nuclei, serving as a relay for nerve impulses traveling between the spinal cord and brainstem and the cerebral cortex. Specific areas of the body surface and cerebral cortex are related to specific parts of the thalamus. Many structural and functional regions of the thalamus have been identified, including the dorsomedial nucleus, the lateroventral nucleus, and the ventroposterior nucleus. See also epithalamus; subthalamus.' - APA


(pl. Tecta)

'the roof of the midbrain, dorsal to the cerebral aqueduct. The tectum contains the superior colliculi, which act as relay and reflex centers for the visual system, and the inferior colliculi, which are sensory centers for the auditory system.' - APA


'a mass of gray matter, forming part of the diencephalon of the brain, whose two lobes form the walls of the third ventricle. It consists of a collection of sensory, motor, autonomic, and associational nuclei, serving as a relay for nerve impulses traveling between the spinal cord and brainstem and the cerebral cortex. Specific areas of the body surface and cerebral cortex are related to specific parts of the thalamus. Many structural and functional regions of the thalamus have been identified, including the dorsomedial nucleus, the lateroventral nucleus, and the ventroposterior nucleus. See also epithalamus; subthalamus.' - APA

Unipolar Neuron

'a neuron that has only a single extension of the cell body. This extension divides into two branches, oriented in opposite directions and representing the axon. One end is the receptive pole, and the other is the output zone. Unipolar neurons transmit touch information from the body surface to the spinal cord. Also called monopolar neuron.' - APA


'any of the four interconnected cavities inside the brain, which serve as reservoirs of cerebrospinal fluid. Each of the two lateral ventricles communicates with the third ventricle via the interventricular foramen; the third and fourth ventricles communicate with each other via the cerebral aqueduct, and with the central canal of the spinal cord and the subarachnoid space. Also called cerebral ventricle.' - APA


'denoting the abdomen or the front surface of the body. In reference to the latter, this term sometimes is used interchangeably with anterior.' - APA

White Matter

'parts of the nervous system composed of nerve fibers that are enclosed in a myelin sheath, which gives a white coloration to otherwise grayish neural structures. The sheaths cover only the fibers, so regions containing mainly cell bodies are gray. ' -APA

Wernicke's Area

'a region toward the back of the superior temporal gyrus of the left hemisphere of the cerebrum containing nerve tissue associated with the interpretation of sounds. Also called Wernicke’s speech area. See also speech area. [Karl Wernicke, who reported, in 1874, a lack of comprehension of speech in patients who had a brain lesion in that area]' - APA