Figure 1.

Cerebellar architecture. The cerebellar cortex harbors five cells types. The PCs are the most obtrusive, appearing as an ordered monolayer located in between the inner granular and the outer molecular cell layer. By providing the only projections to the deep cerebellar and vestibular nuclei, these cells are the sole cerebellar output neurons. Mossy fibers arising from the pontine nuclei, spinal cord and vestibular system project into the granule cell layer to establish synaptic contacts on the granule cells. In turn, PFs arising from granule cells project into the molecular layer to make excitatory synapses on the elaborated dendritic tree of the PC. CFs arising from the inferior olive provide the second PC excitatory innervation. The deep cerebellar nuclei are stimulated by mossy fibers and efferents originating from the inferior olive, while PCs provide inhibitory input.