Extraocular proprioception in electrically induced eye movements

¹ Department of Physiology, University of California Medical Center, Los Angeles, California

Ocular movements evoked by stimulation of brain-stem sites in the feline encéphale isolé have been analyzed in an attempt to demonstrate an extraocular proprioceptive mechanism. Procedures designed to reduce extraocular proprioceptive input to the central nervous system included tenotomy of the muscles of one eye, procaine block of one or both Gasserian ganglia, and acute cerebellectomy. None of these procedures resulted in a consistent alteration in accuracy of the induced oculomotor responses. Immobilization of one eye, however, significantly reduced the accuracy of the freely moving eye in assuming the same final position with repeated stimulation of one site. All procedures tested, including occipital lobectomy, resulted in a significant shift of the final position reached by the eyes in response to repeated stimulation of one site. While the shift, unlike the decrease in accuracy seen with immobilization, cannot be interpreted as evidence for an extraocular proprioceptive mechanism, it is discussed with reference to the significance of the ‘goal’ position obtained by repeated stimulation of one site at constant stimulus parameters.