The regulation of rhythmic locomotion by motor cortical and dopaminergic inputs in the mouse striatum.

The striatum is a critical component of the basal ganglia and plays a central role in regulating motor initiation and action selection. How cortical and subcortical inputs converging at the striatum regulate locomotion remains unclear. By examining gait changes in head-fixed mice running on a treadmill, we found that mice were capable of performing forward, but not backward, rhythmic locomotion using their forelimbs when the striatum and motor cortex were inactivated. The striatal activity is critical for adjusting initially disorganized gait to efficient rhythmic locomotion during forward running training, as well as for increasing the stride width during forward locomotion. The inputs from the motor cortex to striatum are important for the rhythmic locomotion, but not for changes of stride length and width during forward running training. In addition, D1 and D2 dopamine receptor activity in striatum are both important for efficient rhythmic locomotion, while exerting opposite effects on the stride width. Together, these results reveal multifactorial control of efficient and rhythmic gait by motor cortical and dopaminergic inputs converging at the striatum.