Striatonigral control of movement velocity in mice

The basal ganglia have long been implicated in action initiation. Using three‐dimensional motion capture, we quantified the effects of optogenetic stimulation of the striatonigral (direct) pathway on movement kinematics. We generated transgenic mice with channelrhodopsin‐2 expression in striatal neurons that express the D1‐like dopamine receptor. With optic fibres placed in the sensorimotor striatum, an area known to contain movement velocity‐related single units, photo‐stimulation reliably produced movements that could be precisely quantified with our motion capture programme. A single light pulse was sufficient to elicit movements with short latencies (<30 ms). Increasing stimulation frequency increased movement speed, with a highly linear relationship. These findings support the hypothesis that the sensorimotor striatum is part of a velocity controller that controls rate of change in body configurations.