Geometry of visual working memory information in human gaze patterns

Abstract

Stimulus-dependent eye movements have been recognized as a potential confound in decoding visual working memory information from neural signals. Here, we combined eye-tracking with representational geometry analyses to uncover the very information in miniature gaze patterns while participants (n = 41) were cued to maintain visual object orientations. Although participants were discouraged from breaking fixation via real-time feedback, small gaze shifts (< 1 degree) robustly encoded the to-be-maintained stimulus orientation, with evidence for encoding two sequentially presented orientations at the same time. While the orientation encoding upon stimulus presentation was object-specific, it changed to a more object-independent format during cued maintenance, particularly when attention had been temporarily withdrawn from the memorandum. Finally, categorical reporting biases increased after unattended storage, with indications of biased gaze geometries emerging already during the maintenance periods prior to behavioral reporting. These findings disclose a wealth of information in gaze patterns during visuospatial working memory, and suggest systematic changes in representational format when memory contents have been unattended.