Cerebral cortex and cerebellum are thought to interact bidirectionally during movement, motor planning, Pavlovian conditioning, and cognitive function. The pontine nuclei (PN), which consist of the basal pontine nuclei and the reticulotegmental nucleus, constitute the principal hub that convey descending signals from higher brain areas into the cerebellum. The PN receive a massive input from layer 5 of nearly the entire ipsilateral cerebral cortex, and they are thought to serve as a relatively

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... imple relay of this information to both the cerebellar cortex and cerebellar nuclei. Although PN neurons occupy an important anatomical position, little is known about their firing properties during natural movement, feedback effects on cortical activity, or functional role in behavior. Here, we use electrophysiological recordings along with optogenetic and pharmacogenetic perturbations to reveal three key aspects of PN function. First, during the execution of a cortically-dependent reach-to-grab behavior, many PN neurons respond to the movement or to non-motor events, such as the cue signaling trial start. Some neurons respond to both motor and non-motor events, suggesting that the PN do not simply relay separate channels of information into cerebellum, but perform multimodal integration. Second, motor cortical neurons that receive feedback from the ponto-cerebellar system have distinct functional properties during behavior. Third, perturbations of PN function impair performance of reaching, disrupt limb kinematics, and alter the functional responses of motor cortical neurons during movement. Taken together, these results demonstrate that the PN are a rich integrative hub that are essential for dexterous motor control.