Abstract
The effects of interaction between cutaneous and cortically evoked motoneuron activities have been studied in cats. Cortical area stimulated was somatic sensorymotor areas I and II. Motoneuron activities were reflected in recordings from single nerve fibers to a contralateral forearm muscle. The forearm cutaneous nerve on the same side of the recording site was stimulated. The effects were that (i) the latency of the unit discharge became shorter or longer, (ii) the number of unit discharges increased or decreased, and (iii) these effects were mixed. The effects lasted for over 160msec. When cortical stimulation preceded, inhibition mostly occurred at shorter stimulus intervals (up to about 80 msec.) and facilitation, at longer stimulus intervals (over about 80 msec.). When cutaneous stimulation preceded, facilitation mostly occurred at shorter stimulus intervals and inhibition, at shorter and longer stimulus intervals. The preceding cutaneous stimulation dominantly produced facilitatory activities and cortical stimulation, inhibitory activties. The functional significance suggested is that cutaneous sensory information activates cortically induced motor acts which depress the cutaneous reflex.
