Links from complex spikes to local plasticity and motor learning in the cerebellum of awake-behaving monkeys

The hypothesis of cerebellar learning proposes that complex spikes in Purkinje cells engage mechanisms of plasticity in the cerebellar cortex; in turn, changes in the cerebellum depress the simple-spike response of Purkinje cells to a given stimulus and cause the adaptive modification of a motor behavior. Although many elements of this hypothesis have been supported by prior experiments, the links between complex spikes, simple-spike plasticity and behavior have not yet been examined simultaneously during the learning process. We carried out a trial-by-trial analysis of Purkinje cell responses in awake-behaving monkeys and found evidence for a causal role for complex spikes in the induction of cerebellar plasticity during a simple motor learning task. We found that the presence of a complex spike on one learning trial was linked to a substantial depression of simple-spike responses on the subsequent trial, at a time when behavioral learning was expressed.