FACILITATION OF CORTICALLY INDUCED PYRAMIDAL AND EXTRAPYRAMIDAL ACTIVITIES FOLLOWING SKIN NERVE STIMULATION

Abstract

Facilitation of cervicothoracic motoneuron populations of cat was observed when a single shock was delivered to the anterior and the posterior region of somatic area I and somatic area II following a conditioning shock to the contraand ipsilateral superficial radial and saphenous nerve. The greater amplitude of the responses was seen at 10-200 msec. stimulus intervals, although the maximal amplitude was recognized at 25-60 msec. The maximal latency shortening of about 3 msec. was seen at 10-25 msec. stimulus intervals, while the latency shortening of about 1 msec. was observed at 2-10 and 25-200 msec. Similar results were obtained even after the medullary pyramidotomy, indicating that the facilitation of cortically induced activities by a preceding cutaneous volley is caused through the extrapyramidal system. The dosages of nembutal required to block the facilitation were smaller in the pyramidotomized preparations than in the intact preparations, suggesting that cortically induced pyramidal activities also play a role to the facilitation.