PHYSIOLOGICAL AND HISTOLOGICAL CLASSIFICATION OF CEREBELLAR NEURONS ON CHLORALOSE-ANESTHETIZED CATS

Extracellularly isolated neurons in the anterior lobe of the cat cerebellum were divided into 2 subsets based on their pattern of response to peripheral somatosensory input. Members of 1 subset, the E set, responded with a discrete burst of spikes at well-defined latencies to cutaneous stimulation and were not fired antidromically by deep white matter stimulation. The second subset, the I set, appeared to be functionally and anatomically homogeneous. Since I units were located in or near the Purkinje cell layer and some responded at short latencies to deep white matter stimulation and followed such stimulation at high frequencies, they were identified as Purkinje cells. The most prominent feature of I-unit response to peripheral somatosensory input was a cessation of spontaneous firing for several hundred milliseconds. I-unit evoked discharge terminated just before the peak surface-positivity of the peripherally induced cerebellar primary response, whereas E-unit activity in the granular and molecular layers coincided in time with the duration of the surface-positive wave.