VERY SHORT-TERM POTENTIATION OF CLIMBING FIBER EFFECTS ON DEEP CEREBELLAR NUCLEI NEURONS BY CONDITIONING STIMULATION OF MESSY FIBER AFFERENTS

Field potentials induced in deep cerebellar nuclei by the electrical s timulation of contralateral red, pontine and reticularis tegmenti pont is oralis nuclei, the restiform body and the inferior olive were recor ded in the alert cat. Recording sites in interpositus and fastigial nu clei were selected with the aid of antidromic field potentials induced by red nucleus and restiform body stimulation? respectively. Pontine and reticularis tegmenti pontis oralis nuclei stimulation induced smal l, but constant amplitude, field potentials consisting of one or two n egative waves. Control field potentials induced by inferior olive stim ulation consisted of a negative wave at 2-3 ms followed by a late (4-6 ms) positivity. Conditioning stimuli applied to the pontine and retic ularis tegmenti pontis oralis nuclei greatly enhanced the amplitude of the inferior olive-evoked synaptic field potential for a time window of about 40 ms. In contrast, inferior olive conditioning stimulation f ailed to modify the field potentials induced by pontine nuclei stimula tion. These facilitatory effects on field potential amplitude showed n o long-lasting modifications. The transient modification of inferior o live-induced field potentials could be related to attentional movement s made by the animal to natural or electrically-induced sensory cues.