Spontaneous activity of the Purkinje cells in the pigeon cerebellum.

In intact and decerebrate pigeon, both under barbiturate anaesthesia, the spontaneous activity of single Purkinje cells has been analysed. The average frequency of the simple spikes was similar to that described in mammals and was essentially the same in the intact and decerebrate preparations. The average frequency of the complex spikes was higher than that found in mammals and it was significantly depressed in the decerebrate pigeon as compared with the intact one. The amount of the depression, however, was less than that described in mammals. For the simple spikes a correlation was found between the mean interspike interval and both the standard deviation and the percentage of intervals at the mode. The correlation indicates that as the frequency increases the firing tends to become more regular. The same conclusion applies to the complex spikes, although in this case the only significant correlation was between the mean interval and standard deviation. Interval histograms of simple spikes were usually unimodal, but were occasionally also bimodal in both intact and decerebrate pigeons. Interval histograms of complex spikes were usually multimodal with many peaks at regular intervals, the highest peak not necessarily being the first one. The duration of the basic interval varied in different cells from 65 to 130 ms. The probability of firing of the simple spikes is always reduced following the appearance of a complex spike. The duration of the pause is related to the frequency of the simple spikes; the higher the frequency, the shorter the pause. [ABSTRACT FROM AUTHOR]