Paul MacNeilage¹ (), Robert S. Allison², Val Rodriguez¹; ¹University of Nevada, Reno, ²York University

As we move, the images on our retinas move due to head and eye movement, but under normal circumstances we tend to perceive the world as stationary. However, perception of world stationarity will be compromised if there is a significant discrepancy between observed and expected optic flow. This occurs, for example, when getting used to new spectacles, but we normally adapt to these changes. Here we studied the relationship between oculomotor adaptation and perceived stationarity. We adapted observers’ vestibular ocular reflex (VOR) by exposing them to a virtual environment where a fixation point in an otherwise empty world moved with them when they turned their head ~15 deg to the left or right; movement direction on each trial was cued and randomized. The gain of dot motion decreased from 1 to 0.6 over the course of 150 trials. Trials with no fixation point (dark environment) were interspersed to measure VOR adaptation state. Joint analysis of eye and head movements on these trials indicated that many observer’s VOR adapted toward the targeted gain of 0.6. Before and after adaptation we measured each observer’s point of subjective stationarity (PSS), that is the scene motion gain perceived as stationary. On each trial, participants made similar cued head movements in a virtual world composed of a 3D cloud of spheres with a central fixation point and then judged whether the scene appeared to move with or against their head motion. Gain was varied trial to trial according to adaptive staircases to estimate the PSS. Before VOR adaptation, average PSS was not significantly different from a gain of 1, but afterwards, average PSS was significantly less than 1 (p=0.03), indicating that VOR adaptation state influences stationarity perception. This suggests that it may be useful to monitor VOR adaptation state in users of extended reality systems.