Responses of cerebellar Purkinje cells to mechanical perturbations during locomotion of decerebrate cats.

During the locomotion of cats which had been decerebrated at the precollicular and premammillary level, mechanical perturbations (taps of 50-550 g wt.) were applied to the paw dorsum of the left forelimb. Purkinje cells were recorded from the vermis of the cerebellar anterior lobe, and those connected to Deiters' neurons controlling the right forelimb were identified by antidromic and orthodromic stimuli. Taps on the left forelimb induced in these Purkinje cells two types of responses; I-type is a depression of simple spike discharge, often preceded by a brief phase of facilitation, and E-type is entirely a facilitation of simple spike discharge. Complex spikes, representing activation through climbing fiber afferents, were frequently evoked by the taps in both I- and E-types. The I-type depression in Purkinje cells closely corresponds to the previously reported facilitation in Deiters' neurons and forelimb extensor muscles, suggesting that the interlimb coordination during cat's locomotion is effected by linked activity of vermal Purkinje cells and Deiters' neurons.