BASAL GANGLIA - STRUCTURE AND COMPUTATIONS

Until recently the basal ganglia of the mammalian brain have attracted little attention from theoretical neurobiologists. Traditional views of the functioning of the basal ganglia are based on their biomedical importance in disorders such as Parkinson's disease. Their contributio n to normal brain functions has remained poorly understood. Experiment al investigations over the past few decades have produced a wealth of detailed information about the structure of the basal ganglia and the physiological properties of their component neurones. It has become ev ident that the basal ganglia play a role in the selection and performa nce of learnt behaviours, and also in the effects of reinforcement on acquisition and maintenance of new behaviours. At present it is diffic ult to link the symptoms of basal ganglia disorders to these basic fac ts, in part because very few theoretical models attempt to incorporate the information that is now available. Computational modelling can he lp to advance theoretical understanding in this area by establishing e xplicit links between different levels of organization: from the effec ts of neurotransmitters such as dopamine on synaptic plasticity, throu gh the dynamic interactions within subpopulations of neurons, to syste m-level interactions between the basal ganglia and cerebral cortex. Th e aim of this review is to outline existing knowledge of the basal gan glia in relation to previous computer modelling work, and to suggest w ays of making use of the new experimental findings in the next generat ion of models.