Temporal dynamics and representational consequences of the control of processing conflict between visual working memory and visual perception

Visual working memory (WM) extensively interacts with visual perception. When information between the two processes is in conflict, cognitive control can be recruited to effectively mitigate the resultant interference. The current study investigated the neural bases of the control of conflict between visual WM and visual perception. We recorded the electroencephalogram (EEG) from 25 human subjects (13 male) performing a dual task combining visual WM and tilt discrimination, the latter occurring during the WM delay. The congruity in orientation between the memorandum and the discriminandum was manipulated. Behavioral data were fitted to a reinforcement-learning model of cognitive control to derive trial-wise estimates of demand for proactive and reactive control, which were then used for EEG analyses. The level of proactive control was associated with sustained frontal-midline theta activity preceding trial onset, as well as with the strength of the neural representation of the memorandum. Subsequently, discriminandum onset triggered a control prediction error signal that was reflected in a left frontal positivity. On trials when an incongruent discriminandum was not expected, reactive control that scaled with the prediction error acted to suppress the neural representation of the discriminandum, producing below-baseline decoding of the discriminandum that, in turn, exerted a repulsive serial bias on WM recall on the subsequent trial. These results illustrate the flexible recruitment of two modes of control and how their dynamic interplay acts to mitigate interference between simultaneously processed perceptual and mnemonic representations. Significance StatementOne hallmark of human cognition is the context dependent, flexible control of behavior. Here we studied the "mental juggling" required when, while holding information in mind, we have to respond to something that "pops up in front of us" before returning to the interrupted task. Using parameter estimates from a reinforcement-learning model, we analyzed EEG data to identify neural correlates of two discrete modes of cognitive control that act to minimize interference between perception and WM. Proactive control, indexed by frontal midline theta power, increased prior to trial onset when a high level of conflict was expected. Reactive control acted to suppress the representation of items likely to interfere with performance, a processing step with consequences for the subsequent trial.