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Jay Todd, Suk Won Han, Stephenie Harrison, René Marois; The neural correlates of visual working memory consolidation: A time-resolved fMRI study. Journal of Vision 2009;9(8):602. doi: 10.1167/9.8.602.
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The attentional blink (AB) reveals a profound deficit in detecting the second of two temporally proximate targets. It has been argued that the AB results from the capacity-limited process of consolidating information into visual working memory (Chun & Potter, 1995; Jolicoeur, 1998). While a network of parieto-frontal brain regions is believed to play a key role in the AB (Marois et al., 2000, 2004), it is unknown if these regions are involved in working memory (WM) consolidation, as the behavioral model would predict.
Here, we used time-resolved fMRI to isolate brain regions involved in WM consolidation. Subjects performed a visual WM task in which they encoded, in separate blocks of trials, either the color or the face identities of two colored-face stimuli. The stimulus display was shown for 500ms or 1500ms before mask presentation, which were the durations—as determined in pilot experiments—necessary for the consolidation of two colors and two faces, respectively. If a brain region is sensitive to WM consolidation, face-related activity should last longer than color-related activity in the 1500ms condition, reflecting the longer face consolidation time for faces than colors. However, there should be no activity duration difference between faces and colors in the 500ms condition because WM consolidation would be limited to 500ms for the two stimulus conditions. A region-of-interest analysis revealed precisely this pattern of activation in the left posterior lateral prefrontal cortex (LPFC) and bilateral intraparietal sulci (IPS), brain areas previously implicated in the AB. Because subjects were also required to concurrently perform a demanding stimulus-dimming task throughout stimulus presentation, these findings cannot simply be accounted for by differential attention to the displays. Rather, we conclude that these activation results reveal the neural trace of WM consolidation and provide neurobiological support for the consolidation theory of the AB.
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