Influence of saccadic adaptation on spatial localization: comparison of verbal and pointing reports.

Under conditions of short-term saccadic adaptation, stimuli presented long before saccadic onset are perceptually mislocalized in space. Here we study whether saccadic adaptation can also affect localization of objects by pointing. We measured localization performance during fixation and after normal saccades and adapted saccades, for a bar presented well before a saccadic eye movement, for both pointing and verbal localization, under open-loop conditions generated by a transient dark period about 300 ms after the presentation of the bar. During fixation and normal saccade, localization performance for verbal report was veridical, while for pointing there was an overestimation of the target eccentricity respect to gaze, in agreement with the idea of separate representations of space for action and perception. During saccadic adaptation, there was a significant shift of both pointing and verbal report localization in the direction of adaptation with similar spatial selectivity for both tasks. These results indicate that saccadic adaptation induces a similar re-calibration of the action map as well as of the perceptual map, suggesting a common site of operation in the transformation from eye-centered to gaze-centered coordinates.