Tomoya Nakamura^1,2,3, Ikuya Murakami¹; ¹Department of Psychology, The University of Tokyo, ²Center for Brain Science, RIKEN, ³Japan Society for the Promotion of Science

Visual appearance is modulated by spatial context. Orientation repulsion is one such contextual phenomenon wherein a central target appears tilted against the orientation of a surrounding inducer. We employed a psychophysical reverse correlation technique to investigate the temporal window contributing to repulsion at several target–inducer distances. If repulsion results from passive filtering, the window would shift backward with increasing distance due to longer latencies of contextual signals. At 8° below the fixation point, an oriented grating, serving as the inducer, was presented within an annular window and randomly switched the orientation every 33 ms. In the middle of this time sequence, a horizontal target Gabor patch was flashed for 33 ms at the center of the inducer. After they disappeared, two probe Gabor patches, tilted 5° and −5° from the horizontal, were presented side by side, and participants judged which probe appeared closer in orientation to the target. The proportion of judging the target as tilted against the inducer was plotted against the relative time between the target and inducer and then fitted with a Gaussian function. This procedure was separately applied to three blocked conditions for target–inducer distance, defined as the radius of the inducer annulus (2°, 3.5°, and 5°). The temporal window was significantly positive for an inducer orientation of ±20°, consistent with the optimal orientation relationship for repulsion. Contrary to the above prediction, the window significantly shifted forward as distance increased. This shift is considered to reflect the time lag of contextual signals sent from the target to inducer, rather than from the inducer to target. Therefore, contextual modulation in orientation repulsion may be viewed as an active process: after a behaviorally relevant target is detected, query signals radiate from the target representation toward its surrounds to acquire information about the spatial context.

Acknowledgements: Supported by JSPS KAKENHI 21J20400, 22KJ0555, 24KJ0233, 18H05523, 23H01052, and 23K25749.