Influence of sustained visual attention on the prioritization of items within visual working memory

Abstract: Individuals prioritize processing of certain important information based on task demands, which facilitates the processing of prioritized items in Visual Working Memory (VWM). However, the role of sustained visual attention in the prioritized processing of items in VWM remains unclear. Some evidence suggests that visual attention is involved in the prioritized processing of items in VWM, while other evidence indicates a dissociation between visual attention and the prioritized processing of items in VWM. Given the variability in the number of items across VWM tasks in previous studies, our study examined whether the role of sustained visual attention in the prioritized processing of VWM items was modulated by working memory resources. When working memory resources were insufficient, sustained visual attention was required to maintain prioritized items, while it was not required when working memory resources were sufficient. Additionally, we investigated the neural basis of the prioritized processing of items in VWM using the simultaneous acquisition technique of event-related potential and event-related optical signal (ERP-EROS).
Our study included five experiments, with 24, 23, 24, 24, and 17 Chinese participants in Experiments 1a, 1b, 1c, 2 and 3, respectively. In Experiments 1 and 2, a recall report paradigm was used. Participants performed VWM tasks with one prioritized item in Experiment 1 and with two prioritized items in Experiment 2. Additionally, across Experiments 1 and 2, participants performed a visual attention task during the VWM maintenance phase. In Experiment 3, we employed a change detection paradigm. Participants completed VWM tasks with no prioritized items and with one prioritized item, and their brain activity under these different prioritization conditions was recorded.
In Experiment 1, participants were instructed to prioritize processing one VWM item. Visual attention was occupied through single visual attention tasks, double visual attention tasks, and manipulation of the timing of visual attention task presentation (early vs. late). The results consistently indicated that the memory accuracy of non-prioritized items was disrupted by the visual attention task, while prioritized items remained unaffected. In Experiment 2, participants were required to prioritize processing two VWM items, and performed a single visual attention task. We found that both prioritized and non-prioritized items were disrupted by the visual attention task. Results from Experiment 3 revealed that compared to neutral cues with no VWM item prioritization, informative cues indicating prioritization of one item elicited a larger late positive component (LPC) and negative slow wave (NSW), as well as higher activation in the prefrontal and occipital cortices during the maintenance phase.
The results indicated that the role of visual attention in the prioritized processing of items in VWM was modulated by working memory resources. When working memory resources were insufficient, sustained visual attention was required to maintain prioritized items, whereas it was not necessary when working memory resources were sufficient. The neural basis of the prioritized processing of VWM items likely involves the activation of the frontal and occipital cortices during the maintenance phase, as well as the allocation of more working memory resources to enhance the stability of the representation of prioritized items. Our study offers a reasonable explanation for the controversy surrounding the role of visual attention in the prioritized processing of items in VWM in previous research. Furthermore, it sheds further light on the neural mechanisms underlying prioritized processing in VWM from a perspective of high temporal and spatial resolution.