The temporoparietal junction (TPJ) is a key node within the "social brain". Several studies suggest that the TPJ controls representations of the self or another individual across a variety of low-level (agency discrimination, visual perspective taking, control of imitation) and high-level (mentalizing, empathy) sociocognitive processes. We explored whether sociocognitive abilities relying on on-line control of self and other representations could be modulated with transcranial direct current stimulation (tDCS) of TPJ. Participants received excitatory (anodal), inhibitory (cathodal), or sham stimulation before completing three sociocognitive tasks. Anodal stimulation improved the on-line control of self-other representations elicited by the imitation and perspective-taking tasks while not affecting attribution of mental states during a self-referential task devoid of such a requirement. Our findings demonstrate the efficacy of tDCS to improve social cognition and highlight the potential for tDCS to be used as a tool to aid self-other processing in clinical populations.

Previous studies using the dot perspective task have shown that adults are slower to verify the number of dots they can see in a picture when a human figure in the picture, an avatar, can see a different number of dots. This "self-consistency effect," which occurs even when the avatar's perspective is formally task-irrelevant, has been interpreted as evidence of implicit mentalizing; that humans can think about the mental states of others via dedicated, automatic processes. We tested this interpretation by giving participants 2 versions of the dot perspective task. In some trials, the avatar was presented as in previous experiments, and in other trials the avatar was replaced by an arrow with similar low-level features. We found self-consistency effects of comparable size in the avatar and arrow conditions, suggesting that self-consistency effects in the dot perspective task are due to domain-general processes such as those that mediate automatic attentional orienting.

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Although neuroimaging studies have consistently identified the temporoparietal junction (TPJ) as a key brain region involved in social cognition, the literature is far from consistent with respect to lateralization of function. For example, during theory‐of‐mind tasks bilateral TPJ activation is found in some studies but only right hemisphere activation in others. Visual perspective‐taking and imitation inhibition, which have been argued to recruit the same socio‐cognitive processes as theory of mind, are associated with unilateral activation of either left TPJ (perspective taking) or right TPJ (imitation inhibition). The present study investigated the functional lateralization of TPJ involvement in the above three socio‐cognitive abilities using transcranial direct current stimulation. Three groups of healthy adults received anodal stimulation over right TPJ, left TPJ or the occipital cortex prior to performing three tasks (imitation inhibition, visual perspective‐taking and theory of mind). In contrast to the extant neuroimaging literature, our results suggest bilateral TPJ involvement in imitation inhibition and visual perspective‐taking, while no effect of anodal stimulation was observed on theory of mind. The discrepancy between these findings and those obtained using neuroimaging highlight the efficacy of neurostimulation as a complementary methodological tool in cognitive neuroscience.

The control of neurological networks supporting social cognition is crucially important for social interaction. In particular, the control of imitation is directly linked to interaction quality, with impairments associated with disorders characterized by social difficulties. Previous work suggests inferior frontal cortex (IFC) and the temporoparietal junction (TPJ) are involved in controlling imitation, but the functional roles of these areas remain unclear. Here, transcranial direct current stimulation (tDCS) was used to enhance cortical excitability at IFC and the TPJ prior to the completion of three tasks: (i) a naturalistic social interaction during which increased imitation is known to improve rapport, (ii) a choice reaction time task in which imitation needs to be inhibited for successful performance and (iii) a non-imitative control task. Relative to sham stimulation, stimulating IFC improved the context-dependent control of imitation—participants imitated more during the social interaction and less during the imitation inhibition task. In contrast, stimulating the TPJ reduced imitation in the inhibition task without affecting imitation during social interaction. Neither stimulation site affected the non-imitative control task. These data support a model in which IFC modulates imitation directly according to task demands, whereas TPJ controls task-appropriate shifts in attention toward representation of the self or the other, indirectly impacting upon imitation.