Exogenous capture of medial-frontal oscillatory mechanisms by unattended conflicting information.

A long-standing debate in psychology and cognitive neuroscience concerns the way in which unattended information is processed and influences goal-directed behavior. Although selective attention allows us to filter out task-irrelevant information, there is a substantial number of unattended, yet relevant, events that must be evaluated in a flexible manner so that appropriate behaviors can succeed. Here we inspected the extent to which unattended conflicting visual information, which cannot be consciously identified, influences behavior and activates medial prefrontal cortex (mPFC) mechanisms of action-monitoring and regulation, traditionally associated with conscious control processes. To that end, we performed two experiments using a novel variant of the Eriksen flanker task in which spatial attention was manipulated, preventing the conscious identification of unattended visual events. The first behavioral experiment was conducted to validate the efficacy of the novel paradigm. In the second experiment, we evaluated electrophysiological correlates of mPFC activity (a frontocentral negative ERP component and medial-frontal theta oscillations) in response to attended and unattended conflicting events. The results of both experiments demonstrated that attended and unattended conflicting stimuli altered subjects' behavior in a similar fashion, i.e. slowing down their reaction times and increasing their error rates. Importantly, the results of the EEG experiment showed that unattended conflicting stimuli, similarly to attended conflicting stimuli, led to an increase in theta-related frontocentral ERP activity and medial-frontal theta power, irrespective of the degree of conscious representation of the sources of conflict. This study provides evidence that medial-frontal theta oscillations represent a neural mechanism through which the mPFC may suppress and regulate potentially inappropriate actions that are automatically triggered by conflicting environmental stimuli to which we are oblivious.