Visual-vestibular interaction in progressive supranuclear palsy

We measured the stability of gaze during horizontal head rotations at 1-3 H z in four patients with progressive supranuclear palsy (PSP), while they vi ewed a stationary target. Median gain of compensatory eye movements was 0.9 4, similar to control subjects. During rotation in darkness, median gain of vestibule-ocular reflex (VOR) was 0.885 similar to controls. Conversely, t he median gain of smooth-pursuit eye movements at 1.0 Hz was 0.23, lower th an controls. A simple superposition model of smooth pursuit and the VOR cou ld not account for the observed gaze stability during fixation. Our results are further evidence that a visually mediated mechanism, independent of sm ooth pursuit, optimizes eye movements to compensate for head rotations. (C) 2000 Published by Elsevier Science Ltd.