A neural model of working memory processes in normal subjects, Parkinson'sdisease and schizophrenia for fMRI design and predictions

A computational model was previously developed to investigate the role of p arallel basal ganglia-thalamocortical loops in solving tasks that rely on w orking memory. Different lesions are applied to the model in order to inves tigate the working memory deficits observed in Parkinson's disease and schi zophrenia. The simulations predict that the working memory deficits observe d in Parkinson's disease result from a local dysfunction within the brain d ue to a problem in the disinhibitory process arising from the basal ganglia . They also predict that the working memory deficits observed in schizophre nia involve many cortical and subcortical areas and result from a problem i n selecting items in working memory which are stored in basal ganglia-thala mocortical loops. The simulations predict the temporal unfolding of neurona l activity in different brain regions, both in the normal case and in the t wo disease states. A specific event-related functional magnetic resonance i maging study was elaborated to test some of those predictions. (C) 2000 Els evier Science Ltd. All rights reserved.