COGNITIVE PLANNING IN HUMANS - NEUROPSYCHOLOGICAL, NEUROANATOMICAL AND NEUROPHARMACOLOGICAL PERSPECTIVES

In recent years, considerable progress has been made in understanding the cognitive and neuroanatomical basis of high-level planning behavio ur through a combination of neuropsychological, neuropharmacological a nd functional neuroimaging approaches. In this article, early evidence suggesting a relationship between planning impairments and damage to the frontal lobe is reviewed and several contemporary studies of plann ing behaviour in patients with circumscribed frontal lobe excisions ar e described in detail. These neuropsychological investigations, togeth er with recent functional neuroimaging studies of normal control subje cts, have identified a specific area within the mid-dorsolateral front al cortex of humans which appears to be critically involved in the cog nitive processes that mediate efficient planning. The functions of thi s region, both in cognitive planning and in related functions such as working memory, are then discussed in the context of a general theoret ical framework for understanding the functional organization of ''exec utive'' processes within the human lateral frontal cortex. In the fina l sections, the relationship between the planning deficits observed af ter intrinsic frontal lobe damage and those exhibited by patients with neuropathology of primarily subcortical origin, such as Parkinson's d isease, is discussed. A central model for much of this work has been t he concept of corticostriatal circuitry which emphasizes the relations hip between the neocortex and the striatum. The combined evidence from comparative studies in patients and from functional neuroimaging stud ies on Parkinson's disease suggests that altered cortico-striatal inte ractions may disrupt normal planning function at a number of levels, p ossibly consequent upon intrinsic striatal pathology on the one hand a nd the partial loss of(frontal) cortical input to the basal ganglia on the other. (C) 1997 Elsevier Science Ltd.