Abstract

Modification of soleus and anterior tibial anterior horn cell excitability following ipsilateral and contralateral stimulations of the sural nerve was studied by either the H reflex (for the soleus and anterior tibial muscles) or the F response (for the anterior tibial muscles). Several intensities of stimulation were employed. In every instance the recovery curves showed two distinct peaks of facilitation, which appeared with the same delay in muscles with antagonist functions. Also, reciprocal facilitation and inhibition phenomena which occurred after a 25 ms delay and which lasted more than 1000 ms were observed. The intervention of suprasegmentary neuronal mechanisms is proposed to explain the facilitation peaks, while the longer lasting phenomena are probably dependent on spinal processes.