Abstract
Background. Visual performance is not only better at the fovea and decreases with eccentricity, but also has striking polar angle asymmetries: At isoeccentric locations it is better along the horizontal than vertical meridian, and along the lower than upper vertical meridian. Both exogenous (involuntary) and endogenous (voluntary) visual attention uniformly improve performance, preserving these asymmetries. We investigated how presaccadic attention—deployed automatically to the upcoming fixation during saccade preparation—modulates perception around the visual field. We hypothesized that presaccadic attention may benefit performance more where it is worse, thus diminishing the polar angle asymmetries. Method. Observers performed horizontal or vertical saccades to centrally cued targets at the four cardinals (~8.5° eccentricity) and discriminated the orientation of a grating presented just before saccade onset at either the saccade target or the opposite location. We manipulated grating contrast to measure contrast sensitivity and fit contrast response functions to assess contrast-gain (C50) and response-gain (d’max). Results. We (1) replicate polar performance asymmetries during fixation—higher contrast sensitivity along the horizontal than vertical meridian and the lower than upper vertical meridian; (2) document the same polar asymmetries during saccade preparation; and (3) show that presaccadic attention interacts with location: It enhances contrast sensitivity at the horizontal and lower vertical meridian but not at the upper vertical meridian, and results in response-gain at the lower but not the upper vertical meridian. (4) This surprising absence of a performance advantage preceding upwards saccades is not explained by differences in saccade latency or precision. Conclusion. Our findings document a rigid perceptual limitation along the upper vertical meridian, likely due to anatomical constraints. Moreover, they question the generalizability of presaccadic attention measurements made solely along one axis or collapsed across hemifields, and call for a systematic study of eye movements not only across eccentricity but also around the visual field.