SPIKE DISCHARGES OF SINGLE UNITS IN THE CEREBELLAR CORTEX

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Abstract
Spike potentials of single units were recorded from the cerebellar cortex of decerebrated or anesthetized cats through the use of fine wire microelectrodes which circumvent the detrimental influences of cerebellar movement and pressure which make the use of rigid electrodes unsatisfactory. Intrinsic cerebellar neurons were found to be spontaneously active at frequencies ranging from 20-125/sec, with the majority falling in the range of 70-80/sec. This activity occurred in erratic bursts of variable length separated by silent intervals of variable duration. Factors controlling the resting frequency, and the timing of the periods of activity and silence, have not been detd. The identity of the unit producing this activity is unknown. Activity in intrinsic units may be differentiated from activity in extrinsic, or afferent, units through the use of local strychnine and through differences in the responses of the 2 types of units to sensory stimulation. The intrinsic units were active in animals with chronic surgical isolation of areas of the cerebellar cortex. Local strychnine applied to the cerebellar cortex produces characteristic convulsive, avalanching outbursts of activity in intrinsic cerebellar neurons. Similar patterns of activity are also produced by other forms of intense stimulation. Some responses of cerebellar neurons to afferent volleys over spino-cerebellar paths and over cortico-ponto-cerebellar paths are described. It was possible to evoke, to augment and to inhibit activity in cerebellar neurons by such afferent stimulation.