Reciprocal Ia inhibition from the peroneal nerve to soleus motoneurones with special reference to the size of the test reflex.

The aim of the study was to examine the supraspinal control during voluntary movements of the foot in man, of the Ia inhibitory interneurones activated from the anterior tibial muscle and projecting to the soleus alpha-motoneurones. Previous studies have reported an increased inhibition of the soleus alpha-motoneurones by a constant conditioning stimulus to the common peroneal nerve during dorsiflexion of the foot. This was interpreted as a sign of supraspinal facilitation of the Ia inhibitory interneurones. However, these results could not be reproduced in the present study. The contradictory results can probably be explained by some important methodological differences in the use of the H-reflex technique.