Poster F40, Tuesday, March 27, 8:00-10:00 am, Exhibit Hall C
Visual memories bypass normalization
Yurika Watanabe1,2, Ilona M Bloem1,2, Melissa Kibbe1,2, Sam Ling1,2,3; 1Boston University, 2Center for Systems Neuroscience, Boston University, 3Donders Institude for Brain, Cognition and Behavior, Radboud University
How distinct is visual working memory from visual perception? Although evidence suggests that briefly remembered stimuli are represented within early visual cortices, the degree to which these memory traces resemble true visual representations remains unknown. Here, we examined whether visual memory representations succumb to a hallmark neural computation: divisive normalization. The strength of normalization was assessed by utilizing a surround suppression paradigm wherein participants replicated stimulus intensity by means of a method-of-adjustment task. In the first experiment, observers were shown the center and surround stimuli either simultaneously or sequentially followed by a maintenance interval before they were tasked to report the contrast of the center that was held in memory. Results revealed that while there was substantial suppression across the five tested contrast levels (10-75%) in the simultaneous condition, the presence of the surround stimulus during the retention interval had no impact on the quality of the visual memory. We then tested the strength of normalization between two memory representations by asking observers to report either the contrast of the center or the surround, when they were presented simultaneously or sequentially. Again, while we found robust normalization in the simultaneous condition, we found no signature of normalization occurring between multiple memory representations. These results provide unique insight into the nature of visual memory representations, illustrating that while visual memory representations may reside within early visual areas, they are qualitatively distinct from true visual representations, bypassing divisive normalization, a canonical visual computation.
Topic Area: EXECUTIVE PROCESSES: Working memory