THE INFLUENCE OF MUSCLE PAIN ON CORTICALLY INDUCED MOVEMENTS

Abstract

Inj. of a hypertonic NaCl soln. into a muscle or faradization of a muscle which cause muscle pain in man seem to produce similar effects in anesthetized cats. They induce also pupillary dilatation which is due to an inhibition of the tone of the third nerve without involvement of the sympathetic and in some instances vocalization. The effects of cortical stimulation were altered under the influence of these afferent stimuli provided that they produced pupillary dilatation. Under their influence the effect of stimu-lation of the motor cortex was either intensified or qualitatively altered so that different movements were substi-tuted temporarily for those obtained under control conditions. The intensification may be associated with a greater cortical spread so that more muscle groups are involved in the cortical reaction than in the preceding and following control experiments. Ipsilateral movements likewise appeared under the influence of muscle pain obtained by the inj. of NaCl into muscles actually not involved in the movements observed on electrical stimulation of the cortex prior to the inj. of NaCl. Apparently the action of these afferent impulses is not limited to the contralateral cortex but may likewise modify the reactivity of the ipsilateral cortex to electrical stimulation.