Vergence eye-movement responses to whole-body linear acceleration stimuli in man

Eight human subjects were exposed to periodic linear acceleration stimuli of +/- 1.0 ms-2 at 0.2 Hz and +/- 2.5 ms-2 at 0.3, 0.45 and 0.67 Hz, whilst lying in the supine position on a large-stroke vertical vibration platform. Eye movements were recorded by an infrared corneal reflection technique. In conditions of total darkness, with no visual stimulation, all subjects exhibited eye-movement responses composed of both conjugate and vergence components. Subsequent computer analysis of the vergence eye-movement responses showed that they were periodic and related to subject displacement. In a second experimental condition, a platen-fixed LED matrix fixation target was illuminated 0.91 m vertically above the subject. It was found that fixation upon this target did not abolish the vergence eye-movement response, although it was suppressed by approximately 50%.