Enhanced reward coding and condition-independent dynamics in optogenetically identified corticostriatal neurons in monkeys

The basal ganglia are considered to be the site where cortical sensorimotor and dopaminergic reward information interact to potentiate and select actions. This had led to the assumption that cortical inputs to the basal ganglia encode sensorimotor states rather than reward or choice signals. We tested this hypothesis by studying the coding properties of neurons in the frontal eye field of monkeys that were optogenetically identified as being connected to the basal ganglia. We found that neurons already contained information about expected rewards and selected actions. Further, the reward and condition-independent modulations were stronger in connected neurons than in other neurons in the same area. These findings indicate that reward, choice, and sensorimotor information are integrated already in the inputs to the basal ganglia, implying that the basal ganglia play a role in manipulating rather than generating reward and choice signals.