Perturbation of the right prefrontal cortex disrupts interference control.

Resolving cognitive interference is central for successful everyday cognition and behavior. The Stroop task is a classical measure of cognitive interference. In this task, participants have to resolve interference on a trial-by-trial basis and performance is also influenced by the trial history, as reflected in sequence effects. Previous neuroimaging studies have associated the left and right prefrontal cortex with successful performance in the Stroop task. Yet, the causal relevance of both regions for interference processing remains largely unclear. We probed the functional relevance of the left and right prefrontal cortex for interference control. In three sessions, 25 healthy participants received online repetitive transcranial magnetic stimulation (rTMS) over the left and right dorsolateral prefrontal cortex, and sham stimulation over the vertex. During each session, participants completed a verbal-response Stroop task. Relative to sham rTMS and rTMS over the left prefrontal cortex, rTMS over the right prefrontal cortex selectively disrupted the Stroop sequence effect (i.e., the congruency sequence effect; CSE). This effect was specific to sequential modulations of interference since rTMS did not affect the Stroop performance in the ongoing trial. Our results demonstrate the functional relevance of the right dorsolateral prefrontal cortex for the processing of interference control. This finding points towards process-specific lateralization within the prefrontal cortex. The observed process- and site-specific TMS effect provides new insights into the neurophysiological underpinnings of Stroop task performance and more general, the role of the prefrontal cortex in the processing of interference control.