No evidence for mnemonic modulation of interocularly suppressed visual input

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.