Anna Zier^1,2 (), Philipp Deutsch^1,2, Jochen Kaiser^1,2, Christoph Bledowski^1,2; ¹Institute of Medical Psychology, Goethe University Frankfurt am Main, ²Cooperative Brain Imaging Center (CoBIC), Frankfurt am Main

Previous studies on the neuronal basis of working memory have identified brain regions that temporarily store simple visual features like motion direction or color. In contrast, it remains unknown which brain areas temporarily store information about how those features are bound into an object. Each participant (N=20) performed a behavioral training and four separate functional magnetic resonance imaging (fMRI) sessions. Participants memorized two objects composed of two visual features each: color and motion direction. We manipulated the feature bindings within these objects across trials. To collect a sufficient number of binding repetitions per participant, each feature varied only across three exemplar categories (color: blue, yellow and pink; motion direction: leftwards, rightwards and downwards). Verbal strategies were minimized by slightly jittering color value and motion direction within each category. Together, our procedure allowed to isolate memorized binding information by comparing delay-related fMRI activity patterns between trials in which participants memorized pairs of objects with exactly the same features but the opposite binding. Additionally, the design enabled a comparison of activity patterns between trials that differed in a single feature, thereby isolating feature-specific information. Participants in our study were required to memorize two colors, two motion directions, and their binding on each trial. Despite this high memory load demand, we successfully decoded memory-related information about both motion direction and color from the visual cortex in an analysis of 10 of the 20 participants. Crucially, we were also able to decode the trial-specific binding information from the memory-related visual cortex activity. This novel, yet preliminary, finding indicates that early visual areas can retain specific information both about individual features and about the way these features are bound together.