Abstract
Studies of brain-behaviour interactions in the field of working memory (WM) have associated WM success with activation of a fronto-parietal network during the maintenance stage, and this mainly for visuo-spatial WM. Using an inter-individual differences approach, we demonstrate here the equal importance of neural dynamics during the encoding stage, and this in the context of verbal WM tasks which are characterized by encoding phases of long duration and sustained attentional demands. Participants encoded and maintained 5-word lists, half of them containing an unexpected word intended to disturb WM encoding and associated task-related attention processes. We observed that inter-individual differences in WM performance for lists containing disturbing stimuli were related to activation levels in a region previously associated with task-related attentional processing, the left intraparietal sulcus (IPS), and this during stimulus encoding but not maintenance; functional connectivity strength between the left IPS and lateral prefrontal cortex (PFC) further predicted WM performance. This study highlights the critical role, during WM encoding, of neural substrates involved in task-related attentional processes for predicting inter-individual differences in verbal WM performance, and, more generally, provides support for attention-based models of WM.
Highlights
While completing working memory (WM) tasks, a frontoparietal network, composed of the anterior and posterior intraparietal sulci (IPS) and the lateral prefrontal cortex is consistently activated and has been considered to reflect the core neural substrate of WM [1,2]
With respect to the prefrontal cortex, the dorsolateral prefrontal cortex during WM tasks has been associated with executive control and monitoring processes, and more precisely resistance to proactive interference, while the ventrolateral prefrontal cortex is associated with articulatory rehearsal processes especially in the domain of verbal WM some authors associate this region with proactive interference resolution [11,12,13]
The present study highlights the importance of neural dynamics during the encoding stage for predicting inter-individual differences in verbal WM performance, by showing that, in the context of task-related attentional disruption during WM encoding, encoding-related activity of the left anterior and posterior IPS significantly correlates with subsequent performance during verbal WM retrieval
Summary
While completing working memory (WM) tasks, a frontoparietal network, composed of the anterior and posterior intraparietal sulci (IPS) and the lateral prefrontal cortex is consistently activated and has been considered to reflect the core neural substrate of WM [1,2]. Given the well-documented, large inter-individual differences that characterize WM performance, with typical digit list repetition spans ranging between 5 and nearly twice as much in young adults [3], it is critical to understand how these inter-individual differences in behaviour relate to inter-individual variations in the functional network and underlying cognitive processes that support WM. Many studies agree on the important role of the intraparietal cortex in WM tasks, by showing that the bilateral IPS, in both anterior and posterior parts, is sensitive to memory load during short-term retention tasks, and this for both verbal and visual WM tasks [4,5,6]. With respect to the prefrontal cortex, the dorsolateral prefrontal cortex during WM tasks has been associated with executive control and monitoring processes, and more precisely resistance to proactive interference, while the ventrolateral prefrontal cortex is associated with articulatory rehearsal processes especially in the domain of verbal WM some authors associate this region with proactive interference resolution [11,12,13]
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