CEREBELLAR ACTION POTENTIALS IN RESPONSE TO STIMULATION OF VARIOUS AFFERENT CONNECTIONS

Abstract

Bingle electric shock stimulation of the central ends of peripheral nerves of the upper or lower extremity in decerebrated or anesthetized cats resulted in responses in, the anterior lobe of the corpus cerebelli, pyramis, lobulus simplex, and occasionally in the lobulus paramedianus. The action potential response was recorded with a cathode ray oscillograph and a differential amplifier. A response was obtained in the same lobes if the spinocerebellar tracts were stimulated directly in the mid-thoracic region of the spinal cord. Except for a greater amplitude of response in the, homolateral side, no indication of topographical localization of the upper and lower extremities was seen. The vestibular nerve was stimulated by direct application of electrodes to the exposed eighth nerve in the internal auditory meatus. Responses were found in the flocculus, nodulus, uvula and lingula, and in addition in the fastigial nucleus. Needle electrodes were placed in the pons, and responses to stimulation here were found in the lobulus ansiformis, lobulus paramedianus, declive and tuber vermis, in the paraflocculus, pyramis, lobulus simplex and the superior and caudal parts of the culmen. The greatest responses were obtained in the hemisphere and the middle lobe of the vermis (lngvar). Needle electrodes were similarly placed in the inferior olivary nuclei. Responses to stimulation were obtained in all parts of the cerebellum but the potentials of greatest amplitude were found on the lobulus ansiformis. The potentials present on the lobes contralateral to the olive stimulated were the largest, but a slight homolateral response was seen as well. With identical lead positions the sign of the response was different, depending upon whether the spinal nerves or the inferior olivary nuclei were stimulated. This may represent the response produced by different cortical afferent connections.