SPATIAL AND NONSPATIAL WORKING-MEMORY AT DIFFERENT STAGES OF PARKINSONS-DISEASE

Groups of patients with Parkinson's disease, either medicated or unmed icated, were compared with a matched group of normal control subjects on a computerized battery of tests designed to assess spatial, verbal and visual working memory. In the spatial working memory task, subject s were required to search systematically through a number of boxes to find 'tokens' whilst avoiding those boxes in which tokens had previous ly been found. In the visual and verbal conditions, the subjects were required to search in exactly the same manner, but through a number of abstract designs or surnames, respectively, avoiding designs or names in which a token had previously been found. Medicated Parkinson's dis ease patients with severe clinical symptoms were impaired on all three tests of working memory. In contrast, medicated patients with mild cl inical symptoms were impaired on the test of spatial working memory, b ut not on the verbal or visual working memory tasks. Non-medicated pat ients with mild clinical symptoms were unimpaired on all three tasks. These data are compared with the results of a previous study comparing groups of neurosurgical patients with frontal, temporal or amygdalo-h ippocampectomy excisions on the same three tests of working memory. Ta ken together, the findings suggest that working memory deficits in Par kinson's disease emerge, and subsequently progress, according to a def ined sequence, the evolution of which may be linked to the likely spat iotemporal progression of dopamine depletion within the striatum. in r elation to the terminal distribution of its cortical afferents. (C) 19 97 Elsevier Science Ltd.