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Practice improves peri-saccadic shape judgment but does not diminish target mislocalization

Significance Visual sensitivity is markedly reduced during saccades, and peri-saccadic stimuli are misperceived as being closer to the saccade target. We show here that peri-saccadic shape discrimination improves significantly with practice. Unlike classical training paradigms that lead to better performance despite external masking, this perceptual learning occurs in the presence of natural, self-induced masking due to the eye movement (i.e., saccadic suppression). Improvement is generalized across saccade direction and stimulus location but is specific to the stimulus type and task. In contrast, stimulus mislocalization remains as pronounced. Thus, the representation of stimulus position probably involves an obligatory process triggered by the upcoming saccade. The results point to a dissociation between shape and location representations of peri-saccadic stimuli. Visual sensitivity is markedly reduced during an eye movement. Peri-saccadic vision is also characterized by a mislocalization of the briefly presented stimulus closer to the saccadic target. These features are commonly viewed as obligatory elements of peri-saccadic vision. However, practice improves performance in many perceptual tasks performed at threshold conditions. We wondered if this could also be the case with peri-saccadic perception. To test this, we used a paradigm in which subjects reported the orientation (or location) of an ellipse briefly presented during a saccade. Practice on peri-saccadic orientation discrimination led to long-lasting gains in that task but did not alter the classical mislocalization of the visual stimulus. Shape discrimination gains were largely generalized to other untrained conditions when the same stimuli were used (discrimination during a saccade in the opposite direction or at a different stimulus location than previously trained). However, performance dropped to baseline level when participants shifted to a novel Vernier discrimination task under identical saccade conditions. Furthermore, practice on the location task did not induce better stimulus localization or discrimination. These results suggest that the limited visual information available during a saccade may be better used with practice, possibly by focusing attention on the specific target features or a better readout of the available information. Saccadic mislocalization, by contrast, is robust and resistant to top-down modulations, suggesting that it involves an automatic process triggered by the upcoming execution of a saccade (e.g., an efference copy signal).