TPJ-M1 interaction in the control of shared representations: New insights from tDCS and TMS combined

Abstract There is extensive evidence that perceived and internally planned actions have a common representational basis: action observation can induce an automatic tendency to imitate others. If perceived and executed action, however, are based on shared representations, the question arises how we can distinguish self‐related and other‐related representations. It has been suggested that the control of shared representations involves a neural network centered on the temporo‐parietal junction (TPJ). However, the specific role of the TPJ in controlling shared representations is still not clear. In a conflict situation where participants have to execute action A while observing action B, the TPJ might either facilitate the relevant action A or inhibit the irrelevant action B (mirror response). In the present study, we used transcranial Direct Current Stimulation (tDCS) to condition neural activity in the right temporo‐parietal junction (TPJ). We then analyzed the corticospinal output as indexed by motor‐evoked potentials (MEPs) induced by single‐pulse TMS (spTMS) of the left primary motor cortex (M1) during action observation in the context of a conflict task. Results showed that tDCS‐mediated increased control did not entail the attenuation of the task‐irrelevant response activation: the effect of motor mirroring was not suppressed or reduced. Rather, facilitating TPJ activity via anodal tDCS selectively enhanced the instructed motor plan (self‐related representation). This outcome supports the idea that TPJ plays a critical role in detecting the mismatch between self‐related and other‐related representations and is at work to enhance task‐relevant representations. HighlightsWe investigated the functional interaction between TPJ and M1 in the control of shared representations.TPJ stimulation enhances task‐relevant motor representations as indexed by MEPs analysis.