Short-latency autogenic inhibition (IB inhibition) in human spasticity.

The inhibitory effect of IB interneurons on motoneurons was tested in both legs of six hemiplegic adults. On the normal side, an inhibition of 10 ms, (14.6%) was observed in all cases and was similar to that described previously. On the spastic side, the same technique results in a facilitation of same duration reaching a maximum of 15%. Hence the IB inhibitory effect is, at least functionally, absent in spasticity. Disappearance of IB inhibition is an additional mechanism to be considered in interpreting spasticity.