Postsaccadic visual references generate presaccadic compression of space.
With every rapid gaze shift (saccade), our eyes experience a different view of the world. Stable perception of visual space requires that points in the new image are associated with corresponding points in the previous image. The brain may use an extraretinal eye position signal to compensate for gaze changes, or, alternatively, exploit the image contents to determine associated locations. Support for a uniform extraretinal signal comes from findings that the apparent position of objects briefly flashed around the time of a saccade is often shifted in the direction of the saccade. This view is challenged, however, by observations that the magnitude and direction of the displacement varies across the visual field. Led by the observation that non-uniform displacements typically occurred in studies conducted in slightly illuminated rooms, here we determine the dependence of perisaccadic mislocalization on the availability of visual spatial references at various times around a saccade. We find that presaccadic compression occurs only if visual references are available immediately after, rather than before or during, the saccade. Our findings indicate that the visual processes of transsaccadic spatial localization use mainly postsaccadic visual information.
Lappe
M
M
Department of Zoology and Neurobiology, Ruhr-University Bochum, Germany. lappe@neurobiologie.ruhr-uni-bochum.de
Awater
H
H
Krekelberg
B
B
D005403:Fixation, Ocular; D006801:Humans; D012438:Saccades / Q000502:physiology*; D013028:Space Perception / Q000502:physiology*