Academic journal article Cognitive, Affective and Behavioral Neuroscience

Evidence for Working Memory Storage Operations in Perceptual Cortex

Academic journal article Cognitive, Affective and Behavioral Neuroscience

Evidence for Working Memory Storage Operations in Perceptual Cortex

Article excerpt

Published online: 17 January 2014

© Psychonomic Society, Inc. 2014

Abstract Isolating the short-term storage component of working memory (WM) from the myriad of associated executive processes has been an enduring challenge. Recent efforts have identified patterns of activity in visual regions that contain information about items being held in WM. However, it remains unclear (1) whether these representations withstand intervening sensory input and (2) how communication between multimodal association cortex and the unimodal perceptual regions supporting WM representations is involved in WM storage. We present evidence that the features of a face held in WM are stored within face-processing regions, that these representations persist across subsequent sensory input, and that information about the match between sensory input and a memory representation is relayed forward from perceptual to prefrontal regions. Participants were presented with a series of probe faces and indicated whether each probe matched a target face held in WM. We parametrically varied the feature similarity between the probe and target faces. Activity within face-processing regions scaled linearly with the degree of feature similarity between the probe face and the features of the target face, suggesting that the features of the target face were stored in these regions. Furthermore, directed connectivity measures revealed that the direction of information flow that was optimal for performance was from sensory regions that stored the features of the target face to dorsal prefrontal regions, supporting the notion that sensory input is compared to representations stored within perceptual regions and is subsequently relayed forward. Together, these findings indicate that WM storage operations are carried out within perceptual cortex.

Keywords Working memory . Functional connectivity

Working memory (WM) is a multifaceted cognitive construct that comprises short-term storage, rehearsal, interference resolution, decision-making, and response operations. Edward Smith was one of the early pioneers in the use of functional neuroimaging to understand the physiological basis of WM (Jonides et al., 1993; Smith et al., 1995); his enduring legacy is the emphasis on dissociating these components of WM from one another and isolating their neural properties and substrates (Smith & Jonides, 1998, 1999; Wager & Smith, 2003). A large portion of the effort of isolating WM components has been directed at elucidating the neural basis for the short-term storage of information. Some of the earliest studies used a cognitive-subtraction logic, comparing activity across tasks matched for executive demands, but with differential demands on storage, in order to distinguish storage from rehearsal and executive functions. These studies revealed storage-related activity in posterior regions, although some additionally showed similar activity profiles in prefrontal cortex (PFC; Smith & Jonides, 1998, 1999). These findings are broadly consistent with the finding that storage operations are largely intact in patients with lesions to PFC (D'Esposito & Postle, 1999).

Other attempts to identify the neural substrates of shortterm storage processes have involved the use of different stimulus domains as memoranda (Lepsien & Nobre, 2007; Ranganath, Cohen, Dam, & D'Esposito, 2004), the inclusion of interfering information to tax or disrupt storage (Artchakov et al., 2009; Sakai, Rowe, & Passingham, 2002; Yoon, Curtis, &D'Esposito, 2006), or the manipulation of WM load (Braver et al., 1997;Jha&McCarthy,2000; Jonides et al., 1997;Leung,Seelig,&Gore,2004; Todd & Marois, 2004). The results from this work continue to be equivocal; some studies have emphasized the role of lateral PFC in storage operations and suggested that perceptual regions only transiently represent memoranda (Leung, Gore, & GoldmanRakic, 2002;Munketal.,2002), whereas others have suggested that storage occurs primarily within content-specific posterior regions (Postle, 2006). …

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