[Formals for histogram analysis of Purkinje cell interspike intervals]

A hypothesis has been advanced proposing that the resting discharge of Purkinje cells depends on two factors: 1) tonic excitatory inflow and 2) Puasson's inhibitory inflow. This is why variety of interspike intervals is supposed to be the result of non-regular arrival of inhibitory impulses. From these assumptions an analytical expression was derived allowing to calculate probabilities of interspike intervals of various durations. The histograms of interspike intervals obtained analitically were found to coincide satisfactory with those obtained in experiments (Fig. 3, a, b). The analysis of real histograms based on the presented theory allowed to compare excitatory and inhibitory inflows to individual Purkinje Cells. It was found that, on the average, those cells which had large excitatory inflow, had also large inhibitory one, and vice versa (Fig. 4). It was also found that small decrease (about 20 percent) of excitatory inflow, or corresponding increase of inhibitory inflow, resulted in complete inhibition of most Purkinje cells.