Arianna P. Giguere¹ (), Matthew R. Cavanaugh^2,3, Krystel R. Huxlin^2,3, Duje Tadin², Brett R. Fajen⁴, Gabriel J. Diaz^1,2; ¹Rochester Institute of Technology Center for Imaging Science, ²University of Rochester Center for Visual Science, ³Flaum Eye Institute, University of Rochester Medical Center, ⁴Rensselaer Polytechnic Institute Department of Cognitive Science

Why do some cortically blind (CB) drivers who are missing a quadrant or more of their visual field have trouble maintaining a central lane position (Bowers et al. IOVS 2014), while others do not? A recent driving study in virtual reality showed that most right-sided CBs perform similarly to controls, while most left-sided CBs steer differently (Giguere et al. JoV 2024). Here, we asked whether these steering differences arise from the occlusion of visual information or from noise and/or biases in visual motion processing introduced by CB (Cavanaugh et al. JoV 2015). The steering and gaze behavior of 30 subjects with normal vision (mean age: 19.9 years, SD: 1.35) was recorded in a virtual steering task where artificial occluding “scotomas” were imposed on a quadrant of their visual field. The central five degrees of vision were spared to mimic the sparing present in most CB patients. Turn direction (left/right), turn radius (two non-constant radii), and occlusion quadrant (one of four quadrants or no occlusion) were randomized between trials. Participants were biased in lane position away from the side of the simulated blind field with one exception: lane position was unchanged when turning away from occlusions in the upper quadrants. With respect to eye movements, the occlusion quadrant did not affect average gaze azimuth/elevation, percent fixations on road, or look-ahead distance on road. However, participants made fewer saccades when turning towards an upper quadrant occlusion. This study shows that spontaneous occlusion of visual information in the upper vs lower visual field biases steering, but left vs. right occlusions do not fully account for the differences that arise from left and right-sided CB. Future work should examine the influence of CB adaptation to their visual impairments and the effect of internal processing noise on steering.

Acknowledgements: Research to Prevent Blindness/Lions Clubs International Foundation Low Vision Research Award (LVRA)