SKEW DEVIATION OF THE EYES IN NORMAL HUMAN-SUBJECTS INDUCED BY SEMICIRCULAR CANAL STIMULATION

Computerised video-oculography and scleral search coils were used to r ecord the horizontal, vertical and torsional binocular eye movements o f human subjects exposed to roll oscillation at 0.4 Hz about earth-hor izontal and earth-vertical naso-occipital axes in darkness. The stimul i provoked a dominant torsional ('ocular counter-rolling') response wi th a ratio of peak slow phase eye velocity to stimulus velocity which was not significantly different for earth-horizontal (0.39, SD 0.08) o r earth-vertical axis orientations (0.40, SD 0.08). For all conditions the responses also had a head-vertical component which was disconjuga te ('skew deviation'). The cumulative, vertical, slow phase divergence was 5.8 degrees, SD 1.3 degrees, about upright and 4.3 degrees, SD 0. 6 degrees, when supine. This is the first demonstration that dynamic r oll stimuli provoke a skew deviation in normal human subjects. At the frequency tested, the skew was driven by vertical semicircular canal s timulation.