Responses of cerebellar units to a passive movement in the decerebrate cat.

The responses of mossy fibers (MF), granular cells (GrC) and Purkinje cells (PC) were recorded in the cerebellum of the decerebrate cat during a passive movement about the forepaw wrist joint. Three main discharge patterns containing information about all the static and dynamic parameters of the movement were found. Simultaneous recording of complex spikes (CS) and simple spikes (SS) showed that the activity of PC can be modulated through either MF or CF input channels alone or both together. In the latter case SS and CS discharge most commonly showed an opposite behavior, in which the increase of the frequency of one type of spike was accompanied by a decrease of the frequency of the other type. Both inputs displayed tonic and phasic characteristics and all the qualitative discharge patterns observed. Therefore it was concluded that aside from differences in the discharge frequency, both inputs are able to directly signal peripheral events.