Abstract
A remarkable function of human vision is our ability to maintain stable percepts of the world despite retinal inputs that change dramatically with each eye movement. Although previous studies have demonstrated that neurons in parietal cortex can update or “remap” visual inputs following saccadic eye movements (e.g., Duhamel et al., 1992), relatively little is known about how saccades and remapping interact with spatial attention. In the current study, we examined the behavioral effects of saccades on spatial attention in human observers. Trials began with a fixation dot presented at a pseudorandom location on the computer screen. While participants maintained fixation, a cue briefly appeared at a peripheral location; participants were instructed to hold this location in memory. On “saccade” trials, the fixation dot then moved to a new location, and participants made a corresponding saccade. On “no saccade” trials, subjects simply maintained fixation. After a variable delay, an oriented bar appeared, and participants made a speeded response indicating its orientation. Spatial working memory for the cued location was then queried with a challenging same/different location task. Reaction time (RT) on the orientation task was analyzed on trials in which participants correctly responded in both tasks. On “no saccade” trials, there were significant RT benefits when the oriented bar appeared at the cued location compared to other locations. However, on “saccade” trials, participants exhibited RT benefits when the target appeared at the cue's retinotopic location, now shifted in world coordinates. In fact, at some delays, RT benefits for the retinotopic locations were stronger than those for world coordinate locations, suggesting that the locus of spatial attention is encoded in retinotopic coordinates and shifts in space following saccades. Thus, even when spatial working memory maintains locations in world coordinates, spatial attention appears to operate in a retinotopic frame of reference.
Supported by NIH EY014193 (MC), NSF GRF (JG)