THE 3-DIMENSIONAL HUMAN VESTIBULOOCULAR REFLEX - RESPONSE TO LONG-DURATION YAW ANGULAR ACCELERATIONS

We recorded three-dimensional eye movements during angular acceleratio n steps from 0 to 250 degrees/s at 20 degrees/s(2) about an earth-vert ical axis. Experiments were performed on 27 normal subjects and on 19 patients who had recovered well from unilateral vestibular deafferenta tion on the right or left side, In addition to compensatory horizontal eye movements, significant vertical and torsional eye movement compon ents were elicited. These vertical and torsional eye velocity traces l ed to a shift of the axis of eye velocity away from the axis of head v elocity. Horizontal, vertical, and torsional velocity components showe d clear differences between normals and patients with unilateral vesti bular deafferentation, In normals, the axis of eye velocity tilted bac kward and slightly away from the axis of head velocity, Patients showe d similar, but more pronounced, shifts during rotations toward the int act ear and shifts in the opposite direction for rotations toward the operated ear. Eye velocity traces were analyzed with special considera tion given to the orientation of the axis of eye velocity, We speculat e that the vertical and torsional velocity components may be due to th e effects of Listing's plane, as well as the contributions of the otol ith signals.