What is special about activity in the basal ganglia?
There are two major classes of theories about the basal ganglia. The first class hypothesizes
that the basal ganglia are the site where cortical sensorimotor and dopaminergic reward
information interact to potentiate and select actions. These theories predict that content
specificity of information emerges from within the basal ganglia. The second class of
theories posits that information is manipulated within the basal ganglia through processes
such as dimensionality reduction. These theories are primarily based on the fact that there
is a large reduction in the number of neurons from the input to the output stages of the basal
ganglia. These theories posit that there are changes in the coding properties of neurons
rather than the emergence of content specificity.
In this talk, I will present a set of studies where we analyzed the eye movement system of
monkeys to compare single-neuron activity in the basal ganglia with activity in the
cerebellum and the frontal cortex. We used tasks that manipulated both eye movements
and expected rewards. We found that rather than coding specific sensorimotor or reward
parameters, the basal ganglia were unique in how they coded these parameters, both in
terms 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 than
generating reward and sensorimotor signals.