Abstract
Visual working memory is a brief, capacity-limited store of visual information that is involved in a large number of cognitive functions. To guide one’s behavior effectively, one must efficiently allocate these limited memory resources across memory items. Previous research has suggested that items are either stored in memory or completely blocked from memory access. However, recent behavioral work proposes that memory resources can be flexibly split across items based on their level of task importance. Here, we investigated the electrophysiological correlates of flexible resource allocation by manipulating the distribution of resources amongst systematically lateralized memory items. We examined the contralateral delay activity (CDA), a waveform typically associated with the number of items held in memory. Across three experiments, we found that, in addition to memory load, the CDA flexibly tracks memory resource allocation. This allocation occurred as early as attentional selection, as indicated by the N2pc. Additionally, CDA amplitude was better-described when fit with a continuous model predicted by load and resources together than when fit with either alone. Our findings show that electrophysiological markers of attentional selection and memory maintenance not only track memory load, but also the proportion of memory resources those items receive.
Highlights
Visual working memory is a brief, capacity-limited store of visual information that is involved in a large number of cognitive functions
If attention can be flexibly allocated across items in visual working memory5–7 (VWM), how might this be reflected by neural measures of attention and VWM maintenance? There is evidence that the contralateral delay activity (CDA) is well-described by a saturation model, which predicts a continuous increase in CDA amplitude that saturates as set size becomes larger, instead of increasing discretely and plateauing at memory capacity[17]
Because we manipulated proportion of memory resources per item across all three experiments, and were interested in how behavior changed as a function of resource allocation, behavioural results were collapsed across experiments
Summary
Visual working memory is a brief, capacity-limited store of visual information that is involved in a large number of cognitive functions. When distractors are presented alongside targets in a memory display, lower-capacity individuals exhibit larger CDA amplitudes than those with higher capacities, reflecting the fact that they have encoded and stored more distractors in memory[16] This finding has been taken as evidence that poor filtering efficiency, resulting in unnecessary storage, is a critical determinant of VWM capacity. There is evidence that the CDA is well-described by a saturation model, which predicts a continuous increase in CDA amplitude that saturates as set size becomes larger, instead of increasing discretely and plateauing at memory capacity[17] This finding suggests that the CDA, much like VWM performance, may be more flexibly affected by memory load than previously thought. It is currently unknown whether the CDA is flexibly affected by the prioritization of memory items instead of, or in addition to, changes in memory load
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