Effects of updating visuo-spatial working memory in early visual cortex

Abstract

Visuo-spatial working memory refers to the ability to actively maintain a spatial representation of visual information in order to interact with it. Although supported by a network of frontal and parietal structures, it is hypothesized that storing spatial information relies heavily on visual cortex. Indeed, due to its retinotopical lay-out, visual cortex appears to be an ideal candidate for storing location-specific information. In the current study we investigated whether updating the contents of visuo-spatial working memory (in the absence of visual stimulation) is accompanied by changes in activation in visual cortex. Participants were instructed to remember the exact locations of four presented images. After the images were removed from the screen, participants received a central cue (a word, describing one of the images) that told them to keep only one of the locations in memory. After a retention period a marker would appear and participants had to indicate whether the marker was presented at the exact location of the memorized image. On a number of trials a second cue-word describing one of the other images was presented during the retention period, informing the participants that they had to remember, and would be tested on the location of the image indicated by this word. This resulted in an update of the contents of spatial working memory. BOLD responses were measured during the retention period on each trial. The results show that visual cortex is modulated by spatial working memory in the absence of visual stimulation. Furthermore, updating the contents of spatial working memory leads to retinotopically specific changes in activation in early visual cortex. These results suggest that visual cortex is pivotal for maintaining and updating spatial working memory representations.