Daniel Thayer¹, Yanming Li¹, Thomas Sprague¹; ¹University of California, Santa Barbara

Per the ‘sensory recruitment’ model of working memory (WM), frontal and parietal cortex engage sensory regions which have precise feature selectivity to maintain information in WM during delay periods (Curtis & D’Esposito, 2003; Postle, 2006). Since this model predicts that neural populations with specialized tuning should be recruited during WM maintenance, regions with selectivity for non-spatial features, such as color (hV4/VO1/VO2) and motion (TO1/TO2), should be recruited to maintain color and motion information, respectively, and the populations best suited for robust recruitment are those spatially aligned with the sample stimulus location. Some previous studies have shown that when remembering specific object features, the associated location is automatically encoded (Foster et al., 2017; Pratte & Tong, 2014), while others suggest that features are maintained in a spatially global manner (Ester et al., 2009). Here, we tested whether encoding features in WM results in recruitment and maintenance of activation of spatially tuned populations, or instead if feature representations are encoded globally. Participants viewed a colorful moving dot stimulus at a random location on each trial and were postcued to remember its color or motion. After a 12s delay, they adjusted the relevant feature of a probe stimulus, presented at the sample location, to match the sample. We used multivariate spatial inverted encoding models to quantify multivariate activation patterns. Strikingly, in retinotopic color- and motion-selective regions, reconstructed maps contained no representation of the sample stimulus location during the delay period. In sharp contrast, parietal cortex had a robust delay-period representation of the sample stimulus location, even though location was irrelevant for the task. Together, these results indicate that space is not obligatorily encoded in feature-selective cortices. Rather, it appears that parietal cortex encodes the location of the sample stimulus, potentially instantiating feedback signals to feature-selective regions to bind features to a location.

Acknowledgements: Funding: Alfred P Sloan Research Fellowship, National Eye Institute R01-EY035300