Changes of simple and complex spike activity of cerebellar purkinje cells with sleep and waking

Action potentials of cerebellar Purkinje cells were observed in intact monkeys during sleep and waking. Purkinje cells exhibit two sorts of action potentials, called simple and complex spikes, and these two sorts of spikes were differently affected by sleep. Simple-spike activity (generated by the parallel fiber inputs to the Purkinje cell) was highest during sleep with rapid eye movements as compared with both waking and sleep with electroencephalographic slow waves. In contrast, complex-spike activity (generated by the climbing fiber inputs to the Purkinje cell) was lowest during sleep with rapid eye movements. The complex action potential of the Purkinje cell consists of an initial large spike followed by one or more smaller secondary spikes, and the number of these secondary spikes was found to be independent of the background discharge frequency of the simple spike. This independence suggests a possible role of presynaptic factors rather than the excitability level of the Purkinje cell itself in determining the number of secondary discharges occurring in the complex spike.