Abstract
The displacement of a stimulus is often not perceived when it occurs during a saccade. This "saccadic suppression of image displacement" (SSID) is considered to be an important factor for the maintenance of visual stability across eye movements, because it bridges potential errors in stimulus remapping resulting from inaccuracy of extraretinal information. SSID however also depends on visual and spatial properties of the stimulus. It has been reported for horizontal saccades that intrasaccadic target steps are easier to detect if they occur orthogonal to the direction of the saccade, and that a brief postsaccadic blanking of the target leads to a marked improvement of displacement detection. To investigate the components that affect perceived constancy, we measured SSID for a wide range of saccade directions and different intrasaccadic target step directions. Results showed that intrasaccadic steps orthogonal to saccade direction were indeed more easily detected than collinear steps for saccades in all directions, with this difference being largest for horizontal and vertical saccades. A signal detection analysis showed these effects to be differences in sensitivity, not bias. Sensitivity was unrelated to the magnitude of postsaccadic fixation error showing that trial-to-trial oculomotor error did not contribute to post-saccadic localization. Moreover, when oblique saccades were analyzed, sensitivity to displacement was unrelated to saccade endpoint variability, which contrasts with previous reports. In a second set of experiments the target was blanked for 200ms after the saccade, leading to an increase of sensitivity for displacements by a factor of about 1.4 for all saccade directions.
Meeting abstract presented at VSS 2014