Effect of Saccadic Adaptation on Localization of Visual Targets

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Abstract
Objects flashed briefly around the time of a saccadic eye movement are grossly mislocalized by human subjects, so they appear to be compressed toward the endpoint of the saccade. In this study, we investigate spatial localization during saccadic adaptation to examine whether the focus of compression tends toward the intended saccadic target or at the endpoint of the actual (adapted) movement. We report two major results. First, that peri-saccadic focus of the compression did not occur at the site of the initial saccadic target, but tended toward the actual landing site of the saccade. Second, and more surprisingly, we observed a large long-term perceptual distortion of space, lasting for hundreds of milliseconds. This distortion did not occur over the whole visual field but was limited to a local region of visual space around the saccade target, suggesting that saccadic adaptation induces a visuo-topic remapping of space. The results imply that the mechanisms controlling saccadic adaptation also affect perception of space and point to a strong perceptual plasticity coordinated with the well-documented plasticity of the motor system.