There are two major classes of theories about the basal ganglia. The first class hypothesizesthat the basal ganglia are the site where cortical sensorimotor and dopaminergic rewardinformation interact to potentiate and select actions. These theories predict that contentspecificity of information emerges from within the basal ganglia. The second class oftheories posits that information is manipulated within the basal ganglia through processessuch as dimensionality reduction. These theories are primarily based on the fact that thereis a large reduction in the number of neurons from the input to the output stages of the basalganglia. These theories posit that there are changes in the coding properties of neuronsrather than the emergence of content specificity.In this talk, I will present a set of studies where we analyzed the eye movement system ofmonkeys to compare single-neuron activity in the basal ganglia with activity in thecerebellum and the frontal cortex. We used tasks that manipulated both eye movementsand expected rewards. We found that rather than coding specific sensorimotor or rewardparameters, the basal ganglia were unique in how they coded these parameters, both interms of the signal-to-noise ratio of responses and in the variety of their temporal patterns.These results strongly suggest that the basal ganglia play a role in manipulating rather thangenerating reward and sensorimotor signals.
