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Frank Tong, Rosanne Rademaker, Elias Cohen; Working memory for complex objects revealed by fMRI decoding of human visual cortical activity. Journal of Vision 2012;12(9):1271. doi: 10.1167/12.9.1271.
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Recent neuroimaging studies have found that activity patterns in early visual areas contain content-specific information about the basic visual features that observers are maintaining in visual working memory (Harrison & Tong, 2009; Serences et al., 2009). In the present study, we used multivariate pattern analysis (MVPA) to investigate the role of early visual areas and higher order object-selective areas in working memory for complex objects. On each trial, participants were briefly presented with a specific face and a specific house in randomized order, followed by a central numerical cue indicating which object to retain in working memory. After a 15-s retention interval, a test image from the cued object category was presented, and participants reported whether the test image matched or differed from the initial sample. We analyzed the activity patterns in early visual areas (V1-V4) and object-selective areas (fusiform face area, parahippocampal place area) to predict the category retained in working memory. Reliable information about the remembered object category was found in early visual areas and also object-selective areas. Moreover, an individual time point analysis indicated that this information was actively maintained throughout the 15-s delay period. Remarkably, this object-specific information was preserved despite the fact that overall BOLD activity levels dropped below that of fixation baseline during the delay period. Our results indicate that activity patterns in early visual areas can serve to maintain content-specific information about remembered objects, and that previous fMRI studies may have failed to detect the role of early visual areas due to the lack of an overall increase in BOLD response during working memory delays. These findings suggest that the visual working memory system relies on distributed representations throughout the human visual pathway, including early visual areas, to maintain detailed information about visual objects.
Meeting abstract presented at VSS 2012
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