Figure 5.

The olivocerebellar loop circuit. (A) Diagram of olivocerebellar circuit. Action potentials in IO neurons (red) are generated at the crest of the subthreshold oscillations; example of subthreshold oscillations is shown in Figure 2C. These elicit complex spikes in Purkinje cells (green) and activate cerebellar nuclear cells (purple and yellow). Purkinje cell output is inhibitory to cerebellar nuclear cells where the IPSPs trigger rebound firing in cerebellar nuclear cells. Arrows indicate direction of action potential conduction. (B,C) Synaptic potentials and firing of cerebellar nuclear cells. White matter stimulation (WM stim) at increasing stimulus strength elicits graded EPSP-IPSP sequences. The first sequence (1) is due to direct stimulation of mossy fiber collaterals (EPSP) and Purkinje cell axons (IPSP). The second sequence is due to activation of the climbing fiber system (2) the Purkinje cell IPSP was strong enough to activate the rebound response (3 and spikes). (C) Average of 10 responses showing the timing of the EPSP-IPSP sequences. (Modified from Llinás and Muhlethaler, 1988).