A BASICAL STUDY OF EVOKED ELECTROMYOGRAM

(2) VARIABILITIES OF H-WAVE AMPLITUDE AT PRE-AND POST-PHONATION

Abstract

In this study, it was attempted to clarify the neurophysiological mechanism of voluntary movement (phonation) recording evoked EMG (H-wave) which have been studied by Magladery and others basing on the Hoffman's study about monosynaptic reflex. The indicator was the amplitudes of H-wave which were evoked on M. soleus by stimulation on the afferent nerve fibers contained in N. tibialis. Variations of H-wave amplitudes were plotted in relation to the time elapsed from initiation of phonation and were investigated about the central nervous system in relation to it.
As the results of this study, following conclusions were led;
1) At the stage of pre-phonation period, average values of H-wave amplitude were higher than those of control. This result was understood as impulses which were commanded to contract the muscles for phonation raised alpha motoneurones in reflex arc of lower limbs, simultaneusly.
2) The damping phenomenon of H-wave amplitudes were observed just prior to pre-phonation. But the neurophysiological mechanism of it is unknown in detail, now.
3) The H-wave amplitudes showed the highest value in agreement with initiation of phonation. This phenomenon was called as Jendrassik's Maneuver. This effect was understood that Jendrassik's Maneuver had some functional connection to the reticular formation of brain stem.
4) After the initiation of phonation, the inhibitory phenomenon of H-wave amplitudes (this level was lower than that of control) was observed at most of subjects. The neurological mechanism of this phenomenon is unknown.