Glossary

agraphia	Inability to write. This term may also be used to specify specific disorders of spelling.



alexia	Inability to read.



aphasia	Language impairment due to a brain lesion, in the absence of elementary sensory or motor impairment.



apraxia	A disorder of learned, voluntary movement not due to sensory or elementary motor impairment.



association cortex	According to older, sequential models of cortical processing, the areas of cortex (not devoted to sensory or motor function) where higher-order (associative) processes are represented. Because of our growing understanding of the function of these areas, this term is now seen as insufficiently specific and its use is becoming increasingly infrequent.



brain hypothesis	The idea that the brain is the biological organ that controls behavior and generates experience.



Broca's area	The area of cortex (in the posterior part of the left inferior frontal gyrus) which, when damaged, results in an aphasia characterized by an impairment in speech production, while language comprehension is relatively intact.



cerebral dominance for language	The idea that one hemisphere is involved in a particular function and the other one is not. This concept was first applied globally to the left hemisphere, because of its representation of language. Now it is recognized that each hemisphere is specialized for certain functions and that the two hemispheres often work in collaboration. The term complementary hemispheric specialization has largely supplanted this term.



conduction aphasia	Impaired ability to repeat heard language in the absence of impairment in language comprehension and spontaneous language production.



contra coup effect	When a blow to the head bruises the brain by causing it to be thrust against the side of the skull opposite the side of the blow.



contralateral	On the opposite side.



corpus callosum	The massive fiber tract that forms neural connections between the two cerebral hemispheres.



craniotomy	The surgical opening of the skull.



dissolution	The idea put forth by Hughlings-Jackson that lesions to higher brain centers cause a reversal of the evolutionary development of hierarchical organization within the nervous system. This would account for the fact that lesions to higher centers of the nervous system often result in the release of primitive behaviors (e.g., reflexes) that were previously under the control of those centers.



dualism	The idea that there are two spheres or domains of reality (material and spiritual).



equipotentiality	The idea that all parts of the brain (or all parts of a particular region of the brain, such as the cerebral cortex) contribute equally to complex functions.



hemispheric functional asymmetry	See complementary hemispheric specialization.



hemispheric specialization	See complementary hemispheric specialization.



holism	The idea that the whole brain mediates all functions (in contrast to the idea of localization of function).



idealism	The type of monism that holds that only the spiritual (nonphysical) is real.



intrahemispheric specialization of function	Specialization of function within a hemisphere. The functions of Broca's area and of Wernicke's area exemplify this.



ipsilateral	On the same side.



lesion	A general term meaning any kind of damage or disease.



localization of function	The idea that certain functions take place or are mediated by specific regions of the brain.



mass action	The idea that the magnitude of a particular deficit is related to the extent of damaged neural tissue (rather than to the location of the damaged tissue).



materialism	The type of monism that holds that only the physical is real.



mind-body problem	The question of how the mind and the body are related—whether they are separate domains (i.e., body and spirit) or aspects of one domain (i.e., all matter or all spirit).



modular organization	The idea that different aspects of cognitive or emotional processing are organized relatively independently in different specialized brain regions. The specialization of V4 for color vision and of V5 for the perception of movement are examples of modular organization.



monism	The belief that the solution to the mind-body problem is that only one domain (it may be physical or spiritual) is real.



motor cortex	The area of cortex (just anterior to the central sulcus) that is most directly involved in the implementation of movement. Also called M1.



phrenology	The theory of localization of function developed by Gall and Spurzheim that attempted to relate specific brain functions to specific protrusions of the skull (which were believed to be indices of brain structure).



primary sensory cortex	The area of cortex receiving the major initial input from sensory centers in lower brain areas. For example, V1 receives the major initial input from the lateral geniculate nucleus of the thalamus.



release symptoms	The reemergence or disinhibition, after a cortical lesion, of infantile reflexes that had been under cortical control.



sequential processing	The idea that a complex function is composed of a number of more basic processes that are activated in a sequence.



ventricular hypothesis	The idea that the cerebral ventricles are the site of (that they mediate) specific psychological processes.



visual agnosia	Impairment in the recognition of aspects of the visual world not due to an impairment in elementary components of vision, such as visual acuity.



Wernicke's area	The area of cortex in the parietotemporal region of the left hemisphere that, when damaged, results in Wernicke's aphasia (impaired language comprehension and speech that is fluent but not meaningful).

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