Afferent signals from the extraocular muscles of the pigeon modify the electromyogram of these muscles during the vestibulo-ocular reflex.

There is no general agreement on whether afferent signals from the extraocular muscles play any part in oculomotor control. However, we have previously shown that they modify the responses of cells in the oculomotor control system during the vestibulo-ocular reflex (VOR). If, as we suspect, these signals have an important role in the control of the VOR from moment-to-moment, we should be able to demonstrate similar, functionally significant, modifications at the output of the reflex. We have recorded the electromyographic activity of several extraocular muscles of the right eye during the VOR and while imposing movements on the left eye. We describe how the activity of the muscles, reflected in the electromyogram, is modified in specific ways depending on the parameters of the imposed eye movements. The effects of the extraocular afferent signals on the eye-muscle responses to vestibular drive during the slow phase of the VOR appear to be corrective. Thus the present results provide strong evidence that afferent signals from the extraocular muscles are concerned in the control of the reflex from moment-to-moment, and suggest that the wider question of their role in oculomotor control merits further consideration.