The Role of the Prefrontal Cortex in the Maintenance of Verbal Working Memory: An Event-Related fMRI Analysis.

Abstract

Neuroimaging studies have been inconclusive in characterizing the role of the prefrontal cortex (PFC) for maintaining increasingly larger amounts of information in working memory (WM). To address this question, the authors collected event-related functional MRI data while participants performed an item-recognition task in which the number of to-be-remembered letters was parametrically modulated. During maintenance of information in WM, the dorsolateral and the ventrolateral PFC exhibited linearly increasing activation in response to increasing WM load. Prefrontal regions could not be distinguished from one another on the basis of load sensitivity, but the dorsolateral PFC had stronger functional connectivity with the parietal and motor cortex than the ventrolateral PFC. These results suggest an increasingly important role for the PFC in actively maintaining information as the amount of that information increases.

The basal ganglia circuits, dopamine, and ambiguous word processing: A neurobiological account of priming studies in Parkinson's disease

“…More recently, various neuroimaging studies have also implicated DLPFC in tasks involving a cognitive control component (Cabeza & Nyberg, 2000), especially tasks that call on working memory (D'Esposito et al, 1998). In an item-recognition task in which the number of to-be-remembered letters was manipulated, Narayanan et al (2005) found that the dorsolateral and the ventrolateral PFC exhibited linearly increasing activation in response to increasing working memory load. They proposed that the DLPFC was more directly involved in maintaining information relevant to response selection and execution at retrieval.…”

Dynamic causal modeling of load-dependent modulation of effective connectivity within the verbal working memory network

“…WM tasks consistently recruit cortical regions within the dorsolateral prefrontal cortex (DLPFC, Brodmann Area 9/46), the parietal cortex (PAR, BA7/40) and the dorsal anterior cingulate cortex (ACC, BA32) (Fletcher and Henson, 2001;Wager and Smith, 2003;Nee et al, 2013). Within this network, there is evidence for relative functional specialisation according to process; the DLPFC has been intimately linked to encoding, setting attentional priorities and manipulating information (D' Esposito et al, 2000;Narayanan et al, 2005), the PAR has been associated with maintaining attentional focus and storing information (Jonides et al, 1998;Guerin and Miller, 2011) and the ACC has been implicated in error detection and performance adjustment (Carter et al, 1999).…”

“…To date, attempts to model inter-regional relationships within the WM network have been based on minimizing the discrepancy between observed and implied correlations between regional activations (Honey et al, 2002;Narayanan et al, 2005;Axmacher et al, 2008;Esslinger et al, 2012). Although useful, this approach provides limited information about specific mechanisms through which neuronal circuits respond to WM demands (Ramnani et al, 2004; Kim et al, 2007).…”

Age-Group Differences in Set-Switching and Set-Maintenance on the Wisconsin Card Sorting Task

“…For example, lateral PFC is implicated in Working Memory (Narayanan et al, 2005;Smith & Jonides, 1999), whereas medial PFC is involved in flexible switching between tasks, and in overriding a previously relevant stimulus-response association Ridderinkhof, Ullsperger, Crone, & Nieuwenhuis, 2004;Rushworth, Walton, Kennerley, & Bannerman, 2004). Finally, the ability to inhibit responses was found to rely on the orbitofrontal cortex (e.g., Aron, Fletcher, Bullmore, Sahakian, & Robbins, 2003;Roberts & Wallis, 2000).…”