Fig. 1.

Circuits of the cerebellum that provide excitatory synaptic inputs to Purkinje cells. Two pathways provide excitatory input to Purkinje cells (PC), parallel fibers (PF) and climbing fibers (CF). These inputs arise from granule cells (GC) and cells in the inferior olive (I.O), respectively. PCs integrate these excitatory inputs and send GABAergic projections to the deep cerebellar nuclei (DCN). PFs were stimulated with electrodes positioned in the distal part of the molecular layer, and CF was stimulated with electrodes placed in the granule cell layer. All recordings were carried out in the presence of gamma-aminobutyric acid A receptor antagonist picrotoxin (100 μM).