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

The basal ganglia integrate cortical inputs with dopaminergic signals to potentiate and select actions. The reward-related activity of dopamine neurons is well-studied, but the coding properties of cortical inputs to the basal ganglia remain largely unknown. We examined the activity of neurons in the frontal eye field of monkeys that were optogenetically identified as projecting to the basal ganglia. We found that the projecting neurons contained information about expected rewards and selected actions. The reward-related signal and modulations independent of task condition were stronger in optogenetically identified projecting neurons than in other neurons in the same area. These findings indicate that reward, choice, and sensorimotor information are already integrated into the cortical inputs to the basal ganglia, suggesting that the basal ganglia network integrates reward from both cortical and dopaminergic inputs rather than relying on a dopaminergic source alone. Characterizing the information transmitted between structures is key to studying function. Using optogenetically identified neurons in monkeys, the authors show that cortical projections to the basal ganglia encode expected reward and selected actions.