Abstract
It is known that a tight relationship exists between saccades and attention, and that processing of saccade targets starts well before an eye movement is initiated. Does this bond extend to the scale of the foveola, the small high-resolution region of the retina? This region only covers approximately 1 degree of visual angle but is disproportionately important for human vision. Here we investigate whether microsaccade preparation leads to selective perceptual enhancement at the microsaccade target location within the foveola. While observers (n=6) fixated on a marker, a central saccade cue appeared. Observers were instructed to shift their gaze, via a microsaccade, toward a location 20' away in the direction indicated by the saccade cue. Before a microsaccade was performed, two probes (7'x2' bars) were flashed, one at the cued location and the other at the opposite side. A response cue indicated one of the two locations after the execution of the microsaccade, and observers reported the orientation of the bar previously presented at that position. Performance was assessed separately in the congruent trials in which the microsaccade landed at the response cue location and in the incongruent trials where microsaccades landed at the opposite location. Performance was also tested in neutral trials without saccade cue. Discrimination was enhanced in the congruent trials compared to incongruent and neutral trials (d': 1.8, 1.3, 0.8, in congruent, neutral and incongruent trials, respectively; ANOVA F(2,5) = 19, p=0.0004). This result was not the outcome of a voluntary shift in covert attention; performance was similar in congruent and incongruent trials when observers maintained fixation (d': 1.4 vs. 1.3, p=0.8; t-test). Our findings show that fine spatial vision is enhanced prior to the execution of microsaccades. This enhancement occurs selectively at the future landing position of the microsaccade, while performance at other nearby locations is impaired.
Meeting abstract presented at VSS 2018