![]() Subjects were required to keep gaze on the fixation point throughout the trial. Also stimuli presented orthogonally to the saccades path appear compressed (Kaiser & Lappe, 2004).Ī trial started with the presentation of a fixation point 10° to the left of the screen center on the vertical midline (see Figure 1). Probe stimuli presented on the foveal side of the saccade target appear shifted in saccade direction whereas probe stimuli presented beyond the saccade target appear shifted against saccade direction (Lappe, Awater, & Krekelberg, 2000 Ross, Morrone, & Burr, 1997). Under dim light conditions with a saccade target, perisaccadic test stimuli appear compressed toward the saccade target. Stimuli presented in complete darkness will appear shifted in saccade direction homogeneously across the visual field when shown in the perisaccadic temporal range. The mislocalization starts 70 ms before and peaks at saccade onset. The strongest mislocalization effects occur when probe stimuli are presented at the time of saccade eye movements (Ross, Morrone, Goldberg, & Burr, 2001). Also saccade adaptation, an experimental modification of saccade amplitude, changes the apparent position of stimuli presented at the saccade target position (Schnier, Zimmermann, & Lappe, 2010 Zimmermann & Lappe, 2010, 2011). Visual adaptation to a prolonged exposed stimulus alters the perceived offset of a probe stimulus in a vernier alignment task (McGraw, Roach, Badcock, & Whitaker, 2012 Whitaker, McGraw, & Levi, 1997). Third, adaptation methods have been used to change perceived position. Second, shifts of visual attention modulate the perceived space by repelling visual objects away from the cued position (Suzuki & Cavanagh, 1997). Strong mislocalization effects are seen when the visual objects are shown on top of a moving stimulus (Tse, Whitney, Anstis, & Cavanagh, 2011). Visual objects presented close to a moving pattern are mislocalized towards the direction of motion (Whitney, Westwood, & Goodale, 2003 Whitney & Cavanagh, 2000). A number of studies report shifts of the perceived location of a target away from the location that corresponds to its retinal position and these results challenge the “labeled line” theories for coding of spatial position (Fischer, Spotswood, & Whitney, 2011): First, the perceived position of briefly presented objects is modulated by motion (Whitney, 2002). How the visual system retrieves the position of objects in space is a matter of ongoing research. We hypothesize that the attraction might be explained by the summation of the neural activity distributions of probe and anchor. When the probe dot and anchor were presented with similar brief duration, the more peripheral stimulus always shifted toward the more foveal stimulus independently of their temporal order. No compression occurred when the anchor was presented long before or after the mask. The anchor had to appear briefly before mask onset to attract the probe dot. However, when the probe dot was presented simultaneously with the mask it appeared shifted toward the anchor by as much as 50% of their separation. The probe dot location was perceived nearly veridically when presented long before or after mask onset. Subjects estimated the position of the probe dot in relation to a subsequently presented comparison bar. At various times around mask onset a probe dot was flashed. While subjects kept fixation, a salient visual stimulus (from now on referred to as “anchor”) was presented, followed by a brief whole-field mask. Abstract We report a strong compression of space around a visual anchor presented in the near visual periphery (<5°).
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