A computational model of action selection in the basal ganglia. I. A new functional anatomy

We present a biologically plausible model of processing intrinsic to the ba sal ganglia based on the computational premise that action selection is a p rimary role of these central brain structures. By encoding the propensity f or selecting a given action in a scalar value (the salience), it is shown t hat action selection may be recast in terms of signal selection. The generi c properties of signal selection are defined and neural networks for this t ype of computation examined. A comparison between these networks and basal ganglia anatomy leads to a novel functional decomposition of the basal gang lia architecture into 'selection' and 'control' pathways. The former pathwa y performs the selection per se via a feedforward off-centre on-surround ne twork. The control pathway regulates the action of the selection pathway to ensure its effective operation, and synergistically complements its dopami nergic modulation. The model contrasts with the prevailing functional segre gation of basal ganglia into 'direct' and 'indirect' pathways.