Continuous contributions of the dorsolateral striatum to movement initiation and execution.

Spikes in the dorsolateral striatum (DLS) of the basal ganglia (BG) correlate with forelimb and whole-body movements, but the extent to which they contribute to movement remains unclear. Using behavior-timed optogenetic inhibition in rats performing a lever-release reaction-time task, we found that DLS photoinhibition delayed the initiation of forelimb reaching and lever release; when delivered during ongoing reaching, it also interrupted execution. Inhibition during reward retrieval impaired locomotion, especially turning, reducing movement speed and resulting in less efficient trajectories. By contrast, inhibition before the reward-triggering nose poke had little effect despite substantial preceding DLS activity. These effects were accompanied by bidirectional changes in firing rates in the substantia nigra pars reticulata, a BG output nucleus, and were much weaker when the dorsomedial striatum was perturbed. Together, these findings suggest that execution of many, but not all, learned movement patterns depends continuously on DLS activity.