Figure 4.

CS–CN correlograms show evidence of synaptic connections. A, Evidence of monosynaptic connection between the recorded PC and CN neuron (corresponds to connectivity shown in Fig. 2A). Correlogram level is relatively flat until 1–2 ms after 0 time (time of CS) and then drops precipitously, indicating a strong inhibition caused by the CS in the PC. B, Correlogram showing evidence of synaptic connections to a CN neuron by both the recorded PC and a collateral of the olivocerebellar axon to same PC cell. The correlogram shows a brief excitation followed by an inhibition. C, Example of correlogram showing no evidence of a direct synaptic relationship because inhibition of activity starts well before t = 0, as indicated by the downwardly sloped red dashed line, and there is no deflection of this general trend at any of the required latencies. D, The cumulative percentage of each type of olivocerebellar axon–PC–CN synaptic connection pattern is plotted as a function of CN firing rate. The overlap of the three curves indicates that the probability of identifying each synaptic connectivity pattern as a function of the CN firing rate is essentially the same.