High-fidelity but hypometric spatial localization of afterimages across saccades

Humans typically perceive their visual world as stable and continuous, despite frequent shifts of the retinotopic reference frame caused by saccades. This visual stability is paralleled by afterimage movement across saccades: Although retinotopically stable, afterimages appear to move in egocentric space wherever the eye moves. To investigate the mechanisms underlying this phenomenon, we tasked human observers to localize afterimages relative to briefly flashed probes in complete darkness. This psychophysical tracking of afterimages was accompanied by eye tracking, allowing us to fit a dedicated computational model to accurately predict afterimage movement based on the size of eye movements. The gain of afterimage movement was significantly hypometric, remained unaffected by post-saccadic visual feedback and saccadic adaptation, and was inversely related to saccade gain. These findings suggest that afterimage movement is driven by efference-based, feedforward prediction of visual consequences of saccades and demonstrate the potential of the afterimage-tracking technique for studying visual stability.