Abstract
How does the visual system achieve stable and continuous perception despite the often noisy and ever-changing input it receives? We previously reported (Fischer, Shankey, & Whitney, VSS, 2011) on a newly discovered mechanism that may aid in perceptual stability: visual perception is serially dependent, reflecting an integration of input over the last ten seconds or more. Serial dependence is potentially an efficient means of achieving perceptual continuity over time, but to be useful for tasks like tracking objects and planning saccades, it should be spatially tuned, occurring more strongly within a location in space than across different locations. Whether or how serial dependence is spatially tuned is not yet known. Here, we tested for spatial specificity of serial dependence using an orientation judgment task. Subjects saw a series of Gabor patches with random orientations, separated in time by an average of 5 seconds each, and adjusted a response bar to report the perceived orientation of the Gabor on each trial. For any given pair of successive trials, the Gabors could be in i) the same retinal and spatial (screen-centered) location, ii) the same retinal, but different spatial locations, iii) the same spatial, but different retinal locations, or iv) different retinal and spatial locations. These conditions allowed for two key contrasts reflecting the unique effects of changes in retinotopic and spatiotopic coordinates. We quantified serial dependence as the degree to which errors in subjects’ orientation judgments were biased toward the orientation seen on the previous trial. We found that serial dependence is strongly position tuned, and this tuning is carried mostly by retinotopic selectivity. However, there was a unique and significant selectivity for spatiotopic position as well. These results support the potential function of serial dependence in maintaining stable representations of objects over time.
Meeting abstract presented at VSS 2012