Rhythm makes the world go round: An MEG-TMS study on the role of right TPJ theta oscillations in embodied perspective taking

Abstract

While some aspects of social processing are shared between humans and other species, some aspects are not. The former seems to apply to merely tracking another's visual perspective in the world (i.e., what a conspecific can or cannot perceive), while the latter applies to perspective taking in form of mentally "embodying" another's viewpoint. Our previous behavioural research had indicated that only perspective taking, but not tracking, relies on simulating a body schema rotation into another's viewpoint. In the current study we employed Magnetoencephalography (MEG) and revealed that this mechanism of mental body schema rotation is primarily linked to theta oscillations in a wider brain network of body-schema, somatosensory and motor-related areas, with the right posterior temporo-parietal junction (pTPJ) at its core. The latter was reflected by a convergence of theta oscillatory power in right pTPJ obtained by overlapping the separately localised effects of rotation demands (angular disparity effect), cognitive embodiment (posture congruence effect), and basic body schema involvement (posture relevance effect) during perspective taking in contrast to perspective tracking. In a subsequent experiment we interfered with right pTPJ processing using dual pulse Transcranial Magnetic Stimulation (dpTMS) and observed a significant reduction of embodied processing. We conclude that right TPJ is the crucial network hub for transforming the embodied self into another's viewpoint, body and/or mind, thus, substantiating how conflicting representations between self and other may be resolved and potentially highlighting the embodied origins of high-level social cognition in general.

Dissociable roles for the rTPJ and dmPFC in self-other processing: a HD-tDCS study

“…For the right TPJ, we identified a specific effect of inhibiting the self--perspective during allocentric perspective taking with a greater reliance on embodied mental rotation. Our results provide support for the theory that the rTPJ has a causal role in inhibiting the egocentric perspective during embodied rotation (Wang et al, 2015). As we did not identify a general effect of reducing congruency effects for both self and other processing, our results do not support the theory that rTPJ has a non--specific effect for self--other distinction (Santiesteban et al, 2012).…”

“…A meta--analysis of self--referential processes using fMRI identified the dmPFC as the key region for other--related processes with less evidence for TPJ involvement (Denny, Kober, Wager, & Ochsner, 2012). This would suggest that the rTPJ is not involved in domain general processing of other--related representations and more has a role in either online control (Santiesteban et al, 2012), inhibition of the self or egocentric bias (Payne & Tsakiris, 2017;Soutschek et al, 2016), or embodied rotation (Wang, Callaghan, Gooding--Williams, McAllister, & Kessler, 2015). In a previous study, we identified a polarity specific (anodal v cathodal) modulation of dmPFC function when integrating other representations into self--representations across VPT and episodic memory domains (Martin, Dzafic, Ramdave, & Meinzer, 2017).…”

“…Specifically, the rTPJ is a highly connected region involved in numerous cognitive processes (Mars et al, 2012), including higher--order social tasks such as ToM (Krall et al, 2016). Competing theories state that the role of the rTPJ in social cognition is either to distinguish between self and other representations (Santiesteban et al, 2012;Schurz, Aichhorn, Martin, & Perner, 2013), shifting to the other representation through inhibition of the self (Payne & Tsakiris, 2017;Soutschek, Ruff, Strombach, Kalenscher, & Tobler, 2016), or more specifically, facilitating embodied rotation and allow the self--perspective to be mentally rotated into an alternate location, including that of other people (Wang, Callaghan, Gooding--Williams, McAllister, & Kessler, 2016). Several theories also exist for the role of the dmPFC in social cognition.…”

“…Unlike tasks used in previous studies (e.g. Payne & Tsakiris, 2017;Santiesteban et al, 2012;Wang et al, 2015), this battery allows for other--related processes to be parsed into those related to domain general processing related to another agent, self--inhibition in general, or self--inhibition to facilitate mental rotation and thereby provide causal evidence for the dissociable roles of the dmPFC and rTPJ in self--other processing. We hypothesized dissociable roles for self--other processing, with dmPFC stimulation resulting in increased integration of other into self and rTPJ stimulation increasing the integration of the self into other.…”

Brain oscillations and connectivity in autism spectrum disorders (ASD): new approaches to methodology, measurement and modelling

“…In general the temporal integration windows required for optimal decoding of a social interaction are likely to increase with the complexity of the interaction, requiring ever finer coordination between low frequencies across cortical areas with local high frequency gamma (conforming to Arnal & Giraud, 2012). Recently, the relevance of theta-based networks for high-level social cognition (perspective taking, mentalizing) has indeed been reported (Bögels et al, 2014;Wang et al, 2016), and requires further investigation with ASD participants and finer-grained analysis of local phase and cross-frequency coupling. We hypothesise (Table 4, Hypothesis 8) that low frequency (delta-theta) cross-cortical phase coupling should be affected in ASD in conjunction with reduced local PAC and possibly inter-trial phase coherence during highlevel social cognition.…”