The Medial Frontal Cortex Mediates Self-Other Discrimination in the Joint Simon Task: a tDCS study

Interacting with other individuals confronts cognitive control systems with the problem of how to distinguish between self-generated (internally triggered) and other-generated (externally triggered) action events. Recent neuroscience studies identified two core brain regions, the anterior medial frontal cortex (aMFC) and the right temporo-parietal junction (rTPJ), to be potentially involved in resolving this problem either by enhancing self-generated versus other-generated event representations (via aMFC) and/or by inhibiting event representations that are externally triggered (via rTPJ). Using transcranial direct current stimulation (tDCS), we investigated the role of the aMFC and the rTPJ for the online control of self-generated versus other-generated event representations in a joint Simon task. In two experimental sessions, participants received anodal, cathodal, or sham tDCS (1 mA intensity applied for 20 min), while performing an auditory joint Simon task. In addition to a general performance enhancement during cathodal (inhibitory) and anodal (excitatory) stimulation with increased practice, we found a significantly increased joint Simon effect (JSE) during cathodal stimulation of the aMFC (Experiment 1), as compared to sham stimulation. No modulation of the JSE was found during stimulation of the rTPJ (Experiment 2). By enhancing self-generated event representations the aMFC seems to be crucially involved in resolving the self- other discrimination problem in the joint Simon task.