We examined adaptation to frequent conflict in a flanker task using event-related potentials (ERPs). A prominent model of cognitive control suggests the fronto-central N2 as an indicator of conflict monitoring. Based on this model we predicted (1) an increased N2 amplitude for incompatible compared to compatible stimuli and (2) that this difference in N2 amplitude would be less pronounced under conditions of frequent conflict (high cognitive control). In this model, adaptation to frequent conflict is implemented as modulation of early visual processing. Traditionally, variations in processing selectivity in the flanker task have been related to a zoom lens model of visual attention. Therefore, we further predicted (3) effects of conflict frequency on early visual ERP components of the event-related potential, and (4) generalization of conflict adaptation due to increased conflict frequency in the flanker task to other visuospatial tasks, intermixed within flanker task trials. Frequent conflict was associated with reduced flanker interference in response times (RTs) and error rate. Consistent with the literature, amplitude of the fronto-central N2 was larger and latency of the central P3 longer for incompatible stimuli. Both effects were smaller when conflict was frequent, supporting the notion of fronto-central N2 as indicator of conflict monitoring. Neither amplitude nor latency of the posterior P1, as index of early visual processing, was modulated by conflict frequency. Additionally, conflict frequency in the flanker task did not affect the pattern of RTs in a probe task. In sum, our results suggest that conflict adaptation operates in a task-specific manner and does not necessarily alter early information processing, that is, the spatial focus of visual attention.

Current models of cognitive control assume gradual adjustment of processing selectivity to the strength of conflict evoked by distractor stimuli. Using a flanker task, we varied conflict strength by manipulating target and distractor onset. Replicating previous findings, flanker interference effects were larger on trials associated with advance presentation of the flankers compared to simultaneous presentation. Controlling for stimulus and response sequence effects by excluding trials with feature repetitions from stimulus administration (Experiment 1) or from the statistical analyses (Experiment 2), we found a reduction of the flanker interference effect after high-conflict predecessor trials (i.e., trials associated with advance presentation of the flankers) but not after low-conflict predecessor trials (i.e., trials associated with simultaneous presentation of target and flankers). This result supports the assumption of conflict-strength-dependent adjustment of visual attention. The selective adaptation effect after high-conflict trials was associated with an increase in prestimulus pupil diameter, possibly reflecting increased cognitive effort of focusing attention.

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To process information selectively and to continuously fine-tune selectivity of information processing are important abilities for successful goal-directed behavior. One phenomenon thought to represent this fine-tuning are conflict adaptation effects in interference tasks, i.e., reduction of interference after an incompatible trial and when incompatible trials are frequent. The neurocognitive mechanisms of these effects are currently only partly understood and results from brainimaging studies so far are mixed. In our study we validate and extend recent findings by examining adaption to recent conflict in the classical Stroop task using functional magnetic resonance imaging. Consistent with previous research we found increased activity in a fronto-parietal network comprising the medial prefrontal cortex, ventro-lateral prefrontal cortex, and posterior parietal cortex when contrasting incompatible with compatible trials. These areas have been associated with attentional processes and might reflect increased cognitive conflict and resolution thereof during incompatible trials. While carefully controlling for non-attentional sequential effects we found smaller Stroop interference after an incompatible trial (conflict adaptation effect). These behavioral conflict adaptation effects were accompanied by changes in activity in visual color-selective areas (V4, V4α), while there was no modulation by previous trial compatibility in a visual word-selective area (VWFA). Our results provide further evidence for the notion, that adaptation to recent conflict seems to be based mainly on enhancement of processing of the task-relevant information.

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