A computational model of action selection in the basal ganglia. II. Analysis and simulation of behaviour

In a companion paper a new functional architecture was proposed for the bas al ganglia based on the premise that these brain structures play a central role in behavioural action selection. The current paper quantitatively desc ribes the properties of the model using analysis and simulation. The decomp osition of the basal ganglia into selection and control pathways is support ed in several ways. First, several elegant features are exposed - capacity scaling, enhanced selectivity and synergistic dopamine modulation - which m ight be expected to exist in a well designed action selection mechanism. Th e discovery of these features also lends support to the computational premi se of selection that underpins our model. Second, good matches between mode l globus pallidus external segment output and globus pallidus internal segm ent and substantia nigra reticulata area output, and neurophysiological dat a, have been found which are indicative of common architectural features in the model and biological basal ganglia. Third, the behaviour of the model as a signal selection mechanism has parallels with some kinds of action sel ection observed in animals under various levels of dopaminergic modulation.