Presaccadic Attention Shifts Up- and Downwards: Evidence From the Pupil Light Response.

Abstract

Vision is introspectively stable, yet every eye movement moves the image of the world on the retina. The dominant view states that attention must precede saccades to prepare the brain for the postsaccadic retinal input, which ensures a stable visual experience. A recent surge of studies investigated visual asymmetries around the visual field, including asymmetries in presaccadic attention. Such studies demonstrated benefits of presaccadic attention on task performance for horizontal and downward saccades, but strikingly no such benefit was observed for upward saccades. An absence of upward presaccadic shifts would contrast the dominant view and indicate that presaccadic attention may not be necessary to ensure perceptual continuity. Here, we capitalized on the fact that the pupil light response robustly tracks spatial attention to investigate whether presaccadic attention shifts up- and downwards. We manipulated whether the landing brightness of the ensuing saccade could be prepared for prior to the saccade. Specifically, we either presented brightness patches throughout the trial or only presented these upon saccade onset. In two experiments, we observed earlier pupil light responses for both up- and downward saccades when the landing brightness could be prepared for presaccadically. This shows that presaccadic attention shifted prior to up- and downward saccades and agrees with presaccadic attention being instrumental in realizing a stable visual experience. Reconciling previously contradictory findings, presaccadic attention can be shifted without necessarily yielding perceptual benefits for all facets of visual processing at the attended location. Nevertheless, our findings demonstrate presaccadic attention to shift along the vertical meridian.