Self-motion perception is modulated by eye fixation

09. Januar 2014


As we move through the world we usually move our eyes to maintain fixation on objects of interest. However the consequences of these fixation eye movements for self-motion perception remain unclear. To investigate this question, we compared perceived displacement across world-fixed, body-fixed and free fixation conditions. Participants were translated laterally in two intervals and had to determine whether the second interval was farther or shorter than the first. Movement time was always 0.8s, and the reference movement was always 10cm. Fixation condition (world, body or free) was randomized across trials. Displacement was underestimated in the body-fixed condition, in which the eyes remain stationary, compared to the world-fixed condition, in which the observer must move the eyes to maintain fixation. Furthermore, perceived displacement was greater with near (50 cm) than with far (2 m) world-fixed targets, consistent with the increased version eye movement required to maintain near versus far fixation. Overall, larger eye movements were associated with larger perceived displacements. This interaction is reminiscent of eye position modulations seen in self-motion processing areas like MST.