Suppression of the vestibulo-ocular reflex using visual and nonvisual stimuli.

Purpose

To determine to what extent attention directed toward visual, auditory, somesthetic, and imaginary sources would attenuate the vestibulo-ocular reflex (VOR).

Method

Two prospective studies included 16 (Investigation 1) and 5 (Investigation 2) healthy participants (mean age of 24 years in Investigation 1 and 37 years in Investigation 2). VOR gain was assessed with a commercially available rotary chair and was measured in dark both while the subject was tasked with mental alerting exercises and while not being tasked. VOR suppression was measured for the following conditions: (a) visual suppression, (b) auditory suppression, (c) somatosensory suppression, (d) imaginary visual target suppression, and (e) combined auditory and somatosensory suppression.

Results

Attention directed to visual source attenuated the VOR by approximately 85%. Attention directed toward auditory and somatosensory targets (both separately and combined) and attention directed toward an imaginary target suppressed the VOR between 28% and 44%. The extent of VOR suppression that occurred with attention directed toward various nonvisual stimuli was significantly less than the visual suppression of the VOR. The various nonvisual conditions were not statistically different from one another.

Conclusion

The data suggest that it is possible for typical adults to suppress the VOR in the absence of a visual target. That is, the VOR can be attenuated with attention directed toward chair-fixed visual, auditory, somatosensory, and imaginary targets.