BIPOLAR DISORDER A psychiatric disorder characterized by wild mood swings. Individuals experience manic periods of high energy and creativity and depressed periods of low energy and sadness. Also called manic depressive disorder.
BLACK BOX Before the advent of modern imaging technologies in the 1980s and 1990s, there was no way to peer inside the brain, hence it was likened to a black box. (The phrase is borrowed from electrical engineering.) The black-box approach is also one favored by cognitive psychologists and perceptual psychologists, who draw flow diagrams, or charts that indicate purported stages of information processing in the brain without being burdened by knowledge of brain anatomy.
BLINDSIGHT A condition in some patients who are effectively blind because of damage to the visual cortex but can carry out tasks which would ordinarily appear to be impossible unless they can see the objects. For instance they can point out an object and accurately describe whether a stick is vertical or horizontal, even though they can’t consciously perceive the object. The explanation appears to be that visual information travels along two pathways in the brain: the old pathway and the new pathway. If only the new pathway is damaged, a patient may lose the ability to see an object but still be aware of its location and orientation.
BRAINSTEM The major route by which the cerebral hemispheres send information to and receive information from the spinal cord and peripheral nerves. It also gives rise directly to cranial nerves that go out to muscles of facial expression (frowning, winking, smiling, biting, kissing, pouting, and so forth) and facilitates swallowing and shouting. The brainstem also controls, among other things, respiration and the regulation of heart rhythms.
BROCA’S AREA The region that is located in the left frontal lobe and is responsible for the production of speech that has syntactic structure.
CAPGRAS SYNDROME A rare syndrome in which the person is convinced that close relatives—usually parents, spouse, children or siblings—are imposters. It may be caused by damage to connections between areas of the brain dealing with face recognition and those handling emotional responses. Someone with Capgras syndrome might recognize the faces of loved ones but not feel the emotional reaction normally associated with that person. Also called Capgras delusion.
CEREBELLUM An ancient region of the brain that plays an important role in motor control and in some aspects of cognitive functioning. The cerebellum (Latin for “little brain”) contributes to the coordination, precision, and accurate timing of movements.
CEREBRAL CORTEX The outermost layer of the cerebral hemispheres of the brain. It is responsible for all forms of high(er)-level functions, including perception, nuanced emotions, abstract thinking, and planning. It is especially well developed in humans and to a lesser extent in dolphins and elephants.
CEREBRAL HEMISPHERES The two halves of the brain partially specialized for different things—the left hemisphere for speech, writing, language, and calculation; the right hemisphere for spatial abilities, face recognition in vision, and some aspects of music perception (scales rather than rhythm or beat). A speculative conjecture holds that the left hemisphere is the “conformist,” trying to make everything fit in order to forge ahead, whereas the right hemisphere is your devil’s advocate, or reality check. Freudian defense mechanisms probably evolved in the left hemisphere to confer coherence and stability on behavior.
CLASSICAL CONDITIONING Learning in which a stimulus that naturally produces a specific response (an unconditioned stimulus) is repeatedly paired with a neutral stimulus (a conditioned stimulus). As a result, the conditioned stimulus starts evoking a response similar to that of the unconditioned stimulus. Related to associative learning.
COGNITION The process or processes by which an organism gains knowledge of, or becomes aware of, events or objects in its environment and uses that knowledge for comprehension and problem solving.
COGNITIVE PSYCHOLOGY The scientific study of information processing in the brain. Cognitive psychologists often do experiments to isolate the stages of information processing. Each stage can be described as a black box within which certain specialized computations are performed before the output goes to the next box, so the researcher can construct a flow diagram. The British psychologist Stuart Sutherland defined cognitive psychology as the “ostentatious display of flow diagrams as a substitute for thought.”
COGNITIVE NEUROSCIENCE The discipline that attempts to provide neurological explanations of cognition and perception. The emphasis is on basic science, although there may be clinical spin-offs.
CONE A primary receptor cell for vision located in the retina. Cones are sensitive to color and used primarily for daytime vision.
COTARD SYNDROME A disorder in which a patient asserts that he or she is dead, even claiming to smell rotting flesh or worms crawling over the skin (or some other equally absurd delusion). It may be an exaggerated form of the Capgras syndrome, in which not just one sensory area (such as face recognition) but all sensory areas are cut off from the limbic system, leading to a complete lack of emotional contact with the world and with oneself.
CROSS-MODAL Describes interactions across different sensory systems, such as touch, hearing, and vision. If I showed you an unnameable, irregularly shaped object, then blindfolded you and asked you to pick out the object with your hands from a collection of similar objects, you would use cross-modal interactions to do so. These interactions occur especially in the inferior parietal lobule (especially the angular gyrus) and in certain other structures such as the claustrum (a sheet of cells buried in the sides of the brain that receives inputs from many brain regions) and the insula.
DEFENSE MECHANISMS Term coined by Sigmund and Anna Freud. Information that is potentially threatening to the integrity of one’s “ego” is deflected unconsciously by various psychological mechanisms. Examples include repression of unpleasant memories, denial, rationalization, projection, and reaction formation.
DENDRITE A treelike extension of the neuron cell body. Along with the cell body, it receives information from other neurons.
ELECTROENCEPHALOGRAPHY (EEG) A measure of the brain’s electrical activity in response to sensory stimuli. This is obtained by placing electrodes on the surface of the scalp (or, more rarely, inside the head), repeatedly administering a stimulus, and then using a computer to average the results. The result is an electroencephalogram (also abbreviated EEG).
EPISODIC MEMORY Memory for specific events from your personal experience.
EXAPTATION A structure evolved through natural selection for a particular function that becomes subsequently used—and refined through further natural selection—for a completely novel unrelated function. For example, bones of the ear that evolved for amplifying sound were exapted from reptilian jaw bones used for chewing. Computer scientists and evolutionary psychologists find the idea irritating.
EXCITATION A change in the electrical state of a neuron that is associated with an enhanced probability of action potentials (a train of electrical spikes that occurs when a neuron sends information down an axon).
FRONTAL LOBE One of the four divisions of each cerebral hemisphere. (The other three divisions are the parietal, temporal, and occipital lobes.) The frontal lobes include the motor cortex, which sends commands to muscles on the opposite side of the body; the premotor cortex, which orchestrates these commands; and the prefrontal cortex, which is the seat of morality, judgment, ethics, ambition, personality, character, and other uniquely human attributes.