Discharges of Purkinje cells in the paravermal part of the cerebellar anterior lobe during locomotion in the cat.

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Abstract
Extracellular recordings was made from 124 Purkinje cells in the paravermal part of lobule V of the cerebellum in cats walking steadily at a speed of 0.5 m/s on a moving belt. All cells tested had a tactile receptive field from which simple spikes could be evoked and 96% of these were on the ipsilateral forelimb. Of the cells, 76 were also studied while the animals sat or lay quietly without movement. Complex spikes were discharged at 1-2/s and these were accompanied by simple spikes in 59 cells (78%); in the remaining cells there were no or few simple spikes. The over-all mean discharge rate (including both types of spike) was 37.8 .+-. 27 impulses/s (.+-. SD). During locomotion all cells discharged both types of spike and the over-all mean rate was 57.6 .+-. 29 impulses/s (.+-. SD). In all cells but 1, the frequency of the simple spikes was modulated rhythmically in time with the stepping movements but the phasing relative to the step cycle varied widely between cells. Peak rates also varied widely, the average being 91.5 .+-. 44 impulses/s (.+-. SD). Most cells (63%) generated 1 period of accelerated discharge per step but others generated 2 (35%) or 3 (2%) such periods. Despite the individual variations in discharge timing the population as a whole was considerably more active during the swing than the stance phase of the step cycle in the ipsilateral forelimb (68 impulses/s as compared with 49 impulses/s on average). Thirty-four cells were electrophysiologically identified as lying on the c1 zone of the cortex and 25 as being in the c2 zone. During locomotion, the population activity in the 2 zones differed slightly: activity in the c1 population was phase advanced by approximately 1/10 of the step cycle. The results are discussed, with particular emphasis on the finding that population activity in the Purkinje cells of the c1 zone fluctuated during the step cycle in parallel with that in the part of nucleus interpositus to which they project.