Antidromic latency of the monkey pyramidal tract neuron related to ipsilateral hand movements

During three different motor tasks of finger, wrist and arm movements on either side, 80 pyramidal tract neuron (PTN) activities were recorded in the monkey motor cortex. They were divided into three groups; PTNs related to contralateral movement (contra-PTNs), those related to ipsilateral and contralateral movement (bilateral-PTNs) and those related to ipsilateral movement (ipsi-PTNs). The latency histogram of the antidromic activation was similar for contra-PTNs as well as ipsi- and bilateral-PTNs in the fast PTN group, but most of slow PTNs appeared among contra-PTNs. Intracortical microstimulation (ICMS) was delivered to correlate muscular contraction with PTN activity. Most of slow PTNs were related to proximal muscular contraction and PTNs related to proximal muscles appeared more in ipsi- and bilateral-PTNs than in contra-PTNs.