Differential controls of forelimb versus whole‑body movements by striatum

Neurons in the dorsolateral striatum (DLS) of the basal ganglia (BG) fire spikes that correlate with forelimb or whole-body movements during behavior, but their functional contributions remain debated. Using behavior-timed optogenetic inhibition in rats performing a lever-release reaction-time task, we found that transient DLS inhibition delayed the initiation of forelimb reaching and tone-cued lever release, and interrupted ongoing reaches. By contrast, it slowed whole-body locomotion during reward retrieval and reduced movement path efficiency, particularly during turns. Recordings from substantia nigra pars reticulata (SNr) showed bidirectional firing-rate changes during DLS inhibition, suggesting that altered BG output patterns mediate the behavioral effects. These findings indicate movement-type-specific DLS functions: the DLS facilitates and sustains forelimb initiation and execution while promoting efficient, rapid whole-body locomotion.