The right temporoparietal junction is causally associated with embodied perspective taking

Abstract

<jats:p>Several theories exist pertaining to the role of the right temporoparietal junction (rTPJ) in social cognition. A prominent theory claims the rTPJ is especially associated with embodied processes. In the present study we use high-definition transcranial direct current stimulation (HD-tDCS) to provide evidence that the rTPJ is causally associated with the embodied processes underpinning perspective taking. Eighty-eight young human adults were stratified to receive either rTPJ or dorsomedial prefrontal (dmPFC) anodal HD-tDCS in a sham-controlled, double-blind, repeated-measures design. Perspective tracking (line-of-sight) and perspective taking (embodied rotation) were assessed using a visuo-spatial perspective taking (VPT) task that required understanding <jats:italic>what</jats:italic> another person could see or <jats:italic>how</jats:italic> they see it, respectively. Embodied processing was manipulated by positioning the participant in a manner congruent or incongruent with the orientation of an avatar on the screen. As perspective taking, but not perspective tracking, is influenced by bodily posture, this allows the investigation of the specific causal role for the rTPJ in embodied processing. Crucially, anodal stimulation to the rTPJ increased the effect of bodily posture during perspective taking, whereas no such effects were identified during perspective tracking, thereby providing evidence for a causal role for the rTPJ in the embodied component of perspective taking. Stimulation to the dmPFC had no effect on perspective tracking or taking. Therefore, the present study provides support for theories postulating that the rTPJ is causally involved in embodied cognitive processing relevant to social functioning.</jats:p><jats:sec><jats:title>Significance Statement</jats:title><jats:p>The ability to understand another’s perspective is a fundamental component of social functioning. Adopting another perspective is thought to involve both embodied and non-embodied processes. The present study used high-definition transcranial direct current stimulation (HD-tDCS) and provided causal evidence that the right temporoparietal junction (rTPJ) is involved specifically in the embodied component of perspective taking. Specifically, HD-tDCS to the rTPJ, but not another hub of the social brain (dmPFC), increased the effect of body posture during perspective taking, but not tracking. This is the first causal evidence that HD-tDCS can modulate social embodied processing in a site-specific and task-specific manner.</jats:p></jats:sec>

Effects of non-invasive brain stimulation on visual perspective taking: A meta-analytic study

“…Level-1 VPT does not rely on deliberate movement simulation (Kessler and Thomson, 2010) and only requires participants to trace-the-line of sight between the self and target object (Michelon and Zacks, 2006). Therefore, in contrast to prior theories that proposed a critical role of the rTPJ in embodied processes required by Level-2 VPT (Martin et al, 2020), this result suggests that this region may be more involved in suppressing the egocentric perspective when taking the other’s perspective rather than generally detecting incongruencies or fostering mental self-rotation (Payne and Tsakiris, 2017; Soutschek et al, 2016). Notably, the ability to overcome one’s self-centered perspective implemented in the posterior TPJ was also recruited in choosing delayed and prosocial rewards (Soutschek et al, 2016).…”

“…If a study reported both RT and accuracy, we calculated a combined ES according to Scammacca et al 2014’s recommendations. For two studies (Martin et al, 2020; Wang et al, 2016) that reported effects for different rotation angles and body postures during VPT, we also calculated a combined ES for these conditions. For one study (van Elk et al, 2017) that examined the effects of complex mental body transformation and stimulation sessions (online and offline) on VPT, to ensure its comparability with other studies, we only focused on the z-axis 180-degree condition and combined the ESs of both stimulation sessions.…”

“…Moreover, another study showed that such an improvement could extend to Level-2 allocentric perspective-taking (Martin et al, 2019b). However, there is also opposing evidence in which the rTPJ stimulation increased the impact of perspective discrepancy during Level-1 VPT (Martin et al, 2020). Thus, despite that much effort has been devoted to clarifying the causal relationships between brain regions and VPT, the overall findings to date paint a rather mixed and inconclusive picture.…”

“…As mentioned above, participants may be asked to judge the visibility or location of a target from different perspectives (e.g., self or other), in which distinct underlying cognitive mechanisms may be involved. For example, Level-2 VPT typically requires more embodied processing than Level-1 VPT (Martin et al, 2020). However, there is no consensus yet if stimulating a brain region would selectively influence any VPT conditions.…”

“…However, there is no consensus yet if stimulating a brain region would selectively influence any VPT conditions. Moreover, with a few exceptions (Martin et al, 2019a,b, 2020), most NIBS studies in this field only focused on one brain region, making it difficult to compare the different regions’ roles in VPT.…”