Abstract
Previous research on visual working memory suggests that multiple brain regions, including frontal, parietal and early visual cortex, are involved in maintaining visual information in working memory during a delay period. However, the exact role of each of these areas in visual working memory and their subsequent behavioral relevance have long been under debate. Here, using fMRI and a forward encoding model (Brouwer & Heeger, 2009; 2011; Ester et al., 2013), we directly assess the behavioral relevance of the brain areas involved in visual working memory maintenance during a precision task (Wilken & Ma, 2004). On each trial, subjects were presented with two sequential gratings of different orientations and were cued to remember the orientation of one of the gratings. After a 10 s delay, subjects reported the orientation of the remembered grating by rotating a test grating to match the remembered orientation. The precision of a subject's working memory on a given trial was measured as the angular distance between the orientation of the reported and the to-be-remembered grating. Our results show that population-level orientation tuning functions peak at the remembered orientation, and are retained over memory delay in intraparietal sulcus (IPS) and frontal eye fields (FEF), as well as early retinotopic cortex (V1/V2/V3). Furthermore, as memory precision increases, the model fit of the orientation tuning functions improves and the offset of the tuning from the remembered orientation decreases, indicating that the quality of orientation tuning while sustaining visual information is strongly correlated with working memory precision at the single-subject level. Our findings suggest that feature-selective tuning functions are not only maintained in early visual cortex, but also in higher cortical areas, including IPS and FEF, during a visual working memory task; and additionally the precision of this population tuning is predictive of the precision of one's memory representation.
Meeting abstract presented at VSS 2014