Properties of eye movements induced by activation of neck muscle proprioceptors.

BACKGROUND: We have previously reported that neck muscle vibration can induce visual illusory movements and eye movements under subdued ambient illumination in human subjects with the head and body fixed. The subjects viewed a fixation light with one eye and the other eye was covered. The eye movements were recorded with an infrared system mounted in goggles attached to the head of the subject.
METHODS: In order to further examine the properties of these cervico-ocular reactions and reveal any artefacts in the eye movement recordings, we have studied (1) the effect of increasing the ambient light, which made visual illusory movements disappear, (2) the timing between the illusory movement and the eye movement in subdued light, (3) the effect of viewing the target through a pin-hole, which would reveal artefacts due to head movement, and (4) the effect of mounting the eye movement recording system on the head support, which would allow recording to the absolute eye position change.
RESULTS: The results of these experiments showed no significant difference from those that were reported previously. Eye movements of about the same amplitude were induced in both eyes under all conditions, and there was no time difference in the occurrence of visual illusory movements and eye movements.
CONCLUSION: The results of this study confirm that neck muscle vibration can induce eye position changes. This seems to confirm that the proprioceptive messages originating in the neck muscles are processed together with visual information of eye position in determining gaze direction.