Distortion of perceived visual space after prolonged horizontal eccentric gaze holding.

Eye movements have long been used as a measure of underlying brain function and pathology. Specifically, rebound nystagmus has provided a behavioral window into the adaptive mechanisms of gaze holding. It is an eye movement aftereffect resulting from maintaining gaze eccentrically for a prolonged duration. Upon returning to central fixation, the eyes drift or "rebound" back toward the previously held gaze location, demonstrating an adaptive process. Little is known about how prolonged eccentric gaze holding, and the accompanying adaptation of the oculomotor system, influences the perception of visual space. Here, we used a variant of the landmark task to assess spatial bias (or lack thereof) with and without prior eccentric gaze holding. We found that perceived spatial bias after prolonged eccentric gaze holding was significantly different between gaze holding to the far left (-40 deg) and the far right (+40 deg). We also found that sensitivity in distinguishing relative distances between objects in space was marginally different between the left and right gaze holding conditions. This suggests that perceived visual space is differentially impacted by where gaze was previously held, reflecting a dependence on the history of eye positions.