ABSTRACT
The prefrontal cortex constitutes a considerable proportion of the human cortical mantle, over 29% according to Fuster (1989). It seems probable, therefore, that different prefrontal regions will mediate distinct psychological functions. Indeed, lesions of the prefrontal cortex have been shown to disrupt a variety of psychological functions to produce disorders of movement control, language, problem solving, memory, and affect. Nevertheless, it is widely believed that the prefrontal cortex has a primary, unitary function. This broad unitary function is supposed to involve the supervision or execution of other cognitive processes so as to achieve intended goals (see Luria, 1972; and Shallice, 1982, 1988 for different accounts of this view). Deficits produced by lesions of the prefrontal cortex are interpreted as resulting from various kinds of executive disturbance. The view is clearly compatible with the idea that different prefrontal lesions cause functionally distinct deficits with the proviso that all of these are forms of “dysexecutiveness”. There is, however, surprisingly little evidence to show that different prefrontal lesions cause distinct psychological deficits and, in particular, distinct forms of dysexecutiveness (see Kolb & Whishaw, 1990; Passingham, 1993 for reviews of the deficits found, but see Shallice & Burgess, 1996, for a consideration of how dysexecutiveness may be fractionated).
