Decoding the dynamics of cognitive control: Insights from reach movements and electroencephalography

The congruency sequence effect (CSE) refers to a modulation of current-trial interference by the preceding trial in conflict tasks, such as the Eriksen flanker task, with interference typically reduced after incongruent relative to congruent trials. Although widely attributed to dynamic adjustments in cognitive control, the neural mechanisms and temporal dynamics underlying this effect remain poorly understood. Here, we combined a release-and-press flanker task with EEG decoding to examine how trial congruency and response type shape behavior and neural processing in healthy adults. Behaviorally, the CSE emerged only when responses repeated, highlighting the dominant role of stimulus-response binding over abstract control mechanisms. Neural decoding mirrored the CSE: current-trial congruency was more reliably decoded on repeated-response trials following congruent versus incongruent trials. This neural CSE was stimulus-locked, occurred between 450 and 550 ms post-stimulus onset, and was driven by theta-band activity. More broadly, congruency decoding was particularly robust over frontal channels while cross-temporal generalization indicated transient, sequential neural representations underlying control signals. Together, these findings demonstrate that both behavioral and neural signatures of the CSE are tightly constrained by response repetition and emerge within a narrow temporal window. Reach-based measures and multivariate EEG decoding jointly provide a fine-grained account of when, where, and under what conditions control-related signals unfold after conflict.