Abstract
Is working memory simply the reactivation of perceptual representations? Decoding experiments with fMRI suggest that perceptual areas maintain information about what we have seen in working memory. But is this activity the basis of visual working memory itself? If it is, then perceptual interference during maintenance should impair our ability to remember. We tested this prediction by measuring visual working memory performance with and without interfering mask gratings, presented during the memory delay at the same location as the to-be-remembered stimulus. Participants memorized the orientations of 1-4 sample gratings, which appeared for 800ms. After a 5-second pause, the participants were exposed to a target grating in the same location as one of the sample gratings, and the target grating was rotated either clockwise or counterclockwise relative to the original. The task was to identify the direction of change. The key manipulation was that during the 5-second maintenance period, participants were exposed either to a blank screen, or to a rapidly changing stream of mask gratings in each of the previously occupied positions. We reasoned that if visual working memory relies on early perceptual substrates then exposure to conflicting masks that putatively activate the same substrates should impair performance (relative to no-mask trials). In other words, there should be interference, between the rapidly changing perceptual inputs and the perceptually maintained memory representations at the same retinal location. Contrary to this prediction, there was no difference in performance between the masked and unmasked conditions. We did, however, observe significantly reduced accuracy as a function of set size (the number of sample gratings in a trial). This evidence suggests that representations in early perceptual brain regions may not play a functional role in maintaining visual features.
Meeting abstract presented at VSS 2018