EVIDENCE FOR SOLEUS H-REFLEX DEPRESSION INDUCED BY BALLISTIC HEAD ROTATION

In this study, we described a sequence of changes of the electromyogra phic (EMG) and depression of the soleus (Sol) H-reflex that precede an d follow the onset of ballistic head rotation in freely standing human subjects. During head rotation, a sequence of EMG changes occurred si multaneously in Sol and in biceps femoris muscle (BF). Specifically, c hanges to Sol EMG included deactivations (EMG silent period) and H-ref lex depression coincident with BF excitation. Thus, in the case of bal listic head movement, control commands for anticipatory postural adjus tment appear to excite BF and inhibit Sol in a similar way to that pre viously described for the onset of arm movement.