Abstract
Visual working memory (VWM) allows for keeping visual information available for upcoming goal-directed behavior, while new visual input is processed concurrently. Interactions between the mnemonic and perceptual systems cause VWM to affect the processing of visual input in a content-specific manner: visual input that is initially suppressed from consciousness is detected faster when it matches rather than mismatches the content of VWM. It is currently under debate whether such mnemonic influences on perception occur prior to or after conscious access. To address this issue, we investigated whether VWM content modulates the neural response to visual input that remains suppressed from consciousness. We measured fMRI responses to interocularly suppressed stimuli in 20 human participants performing a delayed match-to-sample task: Participants were retro-cued to memorize one of two geometrical shapes for subsequent recognition. During retention, an interocularly suppressed peripheral stimulus (the probe) was briefly presented, which was either of the cued (memorized) or uncued (not memorized) shape category. We found no evidence that VWM content modulated the neural response to the probe. Substantial evidence for the absence of this modulation was found despite leveraging a highly liberal analysis approach: (1) selecting regions of interest that were particularly prone to detecting said modulation, and (2) using directional Bayesian tests favoring the presence of the hypothesized modulation. We did observe faster detection of memory-matching compared to memory-mismatching probes in a behavioral control experiment, thus validating the stimulus set. We conclude that VWM impacts the processing of visual input only once suppression is mostly alleviated.
Highlights
The visual input to our retinae changes on a moment-to-moment basis
We considered one final possibility that could explain why Visual working memory (VWM) content did not affect the neural response to interocularly suppressed probes in the current fMRI experiment: because different visual features rely on different VWM storage sites (Christophel et al, 2017), it is possible that the shape of a stimulus is disrupted by interocular suppression before it can interact with shape-specific VWM content
We considered the possibility that the null effect observed in the fMRI experiment could be explained by an excessive suppressive strength of the masks, and/or by probe stimuli that were too weak to elicit any kind of perceptual signal, prohibiting them to interact with the contents of VWM
Summary
The visual input to our retinae changes on a moment-to-moment basis. we often need to keep visual representations available after the visual input has changed. Visual working memory (VWM) allows for maintaining visual representations available for subsequent, goal-directed behavior. During VWM maintenance, the visual system generally continues to receive visual input. These mnemonic and perceptual processes co-exist (Rademaker et al, 2019), and interact with one-another: visual input can interfere with representations in VWM (Rademaker et al, 2015; Bettencourt and Xu, 2016; Fang et al, 2020; Li, Liang, Lee, Barense, pre-print), and VWM content enhances the neural response to memory-matching relative to memory-mismatching visual input (Kumar et al, 2009; Gayet et al, 2017). As such, understanding at what stage of visual processing VWM content impacts perception (i.e., before or after conscious access) is vital to our understanding of goal-directed visual search. In this study we investigated whether VWM could impact the processing of non-conscious visual input
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