Abstract
The richness of sensory input dictates that the brain must prioritize and select information for further processing and storage in working memory. Stimulus salience and reward expectations influence this prioritization but their relative contributions and underlying mechanisms are poorly understood. Here we investigate how the quality of working memory for multiple stimuli is determined by priority during encoding and later memory phases. Selective attention could, for instance, act as the primary gating mechanism when stimuli are still visible. Alternatively, observers might still be able to shift priorities across memories during maintenance or retrieval. To distinguish between these possibilities, we investigated how and when reward cues determine working memory accuracy and found that they were only effective during memory encoding. Previously learned, but currently non-predictive, color-reward associations had a similar influence, which gradually weakened without reinforcement. Finally, we show that bottom-up salience, manipulated through varying stimulus contrast, influences memory accuracy during encoding with a fundamentally different time-course than top-down reward cues. While reward-based effects required long stimulus presentation, the influence of contrast was strongest with brief presentations. Our results demonstrate how memory resources are distributed over memory targets and implicates selective attention as a main gating mechanism between sensory and memory systems.
Highlights
We can neither instantaneously perceive nor remember all the visual information we encounter
Prioritization and selection of sensory information for further processing based on a combination of exogenous stimulus features and endogenous factors like task relevance and motivation can be described in terms of selective attention or “priority maps”5–11
We found that reward cues only significantly influenced the accuracy of visual working memory when they were presented during the encoding phase, and not during maintenance or retrieval
Summary
We can neither instantaneously perceive nor remember all the visual information we encounter. Prioritization and selection of sensory information for further processing based on a combination of exogenous stimulus features and endogenous factors like task relevance and motivation can be described in terms of selective attention or “priority maps”5–11 The importance of both bottom-up and top-down influences on encoding of visual information is widely recognized making selective attention a prime candidate to selectively gate visual information into working memory . The probability or precision with which an object is reproduced from working memory can be affected by cues that are presented after the stimuli have already disappeared from the screen These ‘retro-cues’ only have an effect when they reliably indicate which memorandum will be probed, suggesting a shift from a memory mode in which retention resources are distributed over multiple memorized objects to a focused mode in which irrelevant objects in memory are actively ‘forgotten’ and the relevant memory is strengthened . We found that reward cues only significantly influenced the accuracy of visual working memory when they were presented during the encoding phase, and not during maintenance or retrieval
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