The cerebellum encodes and influences the initiation and termination of discontinuous movements

The cerebellum is hypothesized to represent timing information important for organizing salient motor events during periodically performed discontinuous movements. To provide functional evidence validating this idea, we measured and manipulated Purkinje cell (PC) activity in the lateral cerebellum of mice trained to volitionally elicit periodic bouts of stereotyped licking for regularly allocated water rewards. Overall, PC simple spiking modulated during task performance, ramping prior to both lick-bout initiation and termination, two important motor events delimiting movement cycles. The ramping onset occurred earlier for the initiation of un-cued exploratory licking that anticipated water availability relative to licking that was reactive to water allocation, suggesting that the cerebellum is engaged differently depending on the movement context. In a subpopulation of PCs, climbing-fiber-evoked responses also increased during lick-bout initiation, but not termination, highlighting differences in how cerebellar input pathways represent task-related information. Optogenetic perturbation of PC activity disrupted the behavior in both initiating and terminating licking bouts and reduced the ability of animals to finely time predictive action around reward delivery, confirming a causative role in movement organization. Together, these results substantiate that the cerebellum contributes to the control of explicitly timed repeated motor actions.