Adaptive motion processing in bilateral vestibular failure

Background Patients with bilateral vestibular failure (BVF) suffer from oscillopsia during head movements. This is secondary to the loss of the vestibulo-ocular reflex which is responsible for stabilising retinal images during head movements of high frequency or velocity. Previous studies documented decreased visual motion sensitivity in such patients at low velocities. The authors now examine motion coherence tasks, which have two advantages: (1) the task is associated with the functions of the middle temporal area; and (2) it affords testing at low and high motion velocities, as relevant for patients with oscillopsia due to BVF. Methods Nine BVF patients and nine healthy control subjects were examined with a random dot pattern with variable percentages of dots moving in the target direction. Participants were asked to indicate in which of two possible directions they perceived the coherent motion. Horizontal and vertical planes were tested at speeds from 0.156 to 40 degrees/s. Results Motion coherence thresholds were lower at higher speeds in both groups (p