Keeping vision stable: Rapid updating of spatiotopic receptive fields may cause relativistic-like effects

Summary People shift their gaze more frequently than they realize, sometimes smoothly to track objects in motion, more often abruptly with a saccade to bring a new part of the visual field under closer visual examination. Saccades are typically made three times a second throughout most of our waking life, but they are rarely noticed. Yet they are accompanied by substantial changes in visual function, most notably suppression of visual sensitivity, mislocalization of spatial position, and misjudgments of temporal duration and order of stimuli presented around the time. Here we review briefly these effects and expound a novel theory of their cause. To preserve visual stability, receptive fields undergo a fast but not instantaneous remapping at the time of saccades. If the speed of remapping approaches the physical limit of neural information transfer, it may lead to relativistic-like effects observed psychophysically, namely a compression of spatial relationships and a dilation of time. Introduction Saccades are ballistic movements of the eyes made to reposition our gaze. They can be deliberate but normally are automatic and go unnoticed. Not only do the actual eye movements escape notice, but so do the image motion they cause and the fact that gaze itself has been repositioned. This problem has gained the attention of most visual scientists, including von Helmholtz (1866), Sperry (1950), Alhazen (1083), and Howard (1996). A general conclusion to emerge from a variety of studies was that saccades were accompanied by a “corollary discharge” (Sperry 1950) or an “efference copy” (von Holst & Mittelstädt 1954) of the motor signal that corrected for the eye movement (for general review, see Ross et al. 2001).