Neural dissociation of visual working memory consolidation and maintenance

Abstract

Encoding of information into visual working memory (VWM), also known as short-term consolidation, is thought to represent a distinct process from maintenance of information (Jolicoeur & Dell'Acqua, 1998; Woodman & Vogel, 2004). In addition, VWM consolidation has been theorized to occupy a central role in conscious perception. Despite the fact that it has been the focus of much behavioral work, and that it is mechanistically dissociable from VWM maintenance, the neural substrates of VWM consolidation are poorly understood. Here we used functional magnetic resonance imaging (fMRI) to determine whether VWM consolidation is neurally dissociable from VWM maintenance. Participants performed a delayed recognition task that involved encoding and maintaining a variable number of colored discs over a retention interval (9.2s) that was long enough to distinguish encoding-related from maintenance-related activity. In two independent groups of subjects, we observed load-dependent, consolidation-related activity in lateral occipital cortex. By contrast, this brain region showed no maintenance-related activity. Control experiments indicate that the consolidation-related activity cannot be accounted for by perceptual processing. Finally, although several frontal and parietal cortex regions showed evidence of both encoding and maintenance-related activity, none showed consolidation-specific activity. Taken together, these results suggest that VWM consolidation is neurally dissociable from VWM maintenance.