The role of presaccadic compression of visual space in spatial remapping across saccadic eye movements

AbstractWhen multiple bars are briefly flashed near the saccadic goal on a visual reference just before a saccade, the total width of the multiple bars appears to be compressed toward the saccadic goal. We show that presaccadic compression of visual space is related to the attribution of the displacement of a visual stimulus to the displacement of another stimulus appearing after the saccade. Subjects observed a bar and a ruler. The bar was displaced during a saccade and the ruler disappeared briefly at the same time, and then the ruler reappeared at the same location after the saccade. The subjects had the impression that the bar appeared to remain stationary and the ruler appeared to be displaced after the saccade. This impression occurs strongly when the amount of the compression of visual space reaches the maximum at the saccade onset. Also, it occurs only at the saccadic goal in the same way as presaccadic compression of visual space. Saccadic suppression of displacement was equivalent at the saccadic goal and in the location opposite to the saccadic goal, indicating that the attribution of the bar displacement to the displacement of the ruler appearing after the saccade is not a consequence of saccadic suppression of displacement. Furthermore, performing a direction discrimination task showed that the bar appears stationary at the saccadic goal during compression of visual space even when the bar was actually displaced. We interpret these results as showing that presaccadic compression of visual space establishes the location of the saccadic goal (the bar) as a reference and then the location of the ruler is remapped relative to the reference location after the saccade, resulting in the illusory displacement of the ruler