Action-based organization and function of cerebellar cortical microcircuits

The cerebellum is the largest sensorimotor structure in the brain, but its mode of operation is not well understood. However, a fundamental organizational feature of the cerebellar cortex is division into elongated zones, defined by their inputs from specific parts of the inferior olive and Purkinje cell output to cerebellar and vestibular nuclei. Little is known about how the pattern of neuronal activity in zones, and their functional microcircuit subdivisions, microzones, is related to behaviour in awake animals. Here, we studied the organization of microzones within the C3 zone and their activity during a skilled forelimb reaching task in cats. Neurons in different parts of the C3 zone, functionally determined by receptive field characteristics, differed in their patterns of activity during movement. Our results suggest that the cerebellar C3 zone is organized and operates within an action-based frame of reference, with different microcircuits within the zone controlling specific muscle synergies.