Roles of the right temporo‐parietal and premotor cortices in self‐location and body ownership

Abstract

In the rubber hand illusion (RHI), the feeling that a fake hand belongs to oneself can be induced by the simultaneous, congruent touch of the fake visible hand and one's own hidden hand. This condition is also associated with a recalibration of the perceived location of the real hand. A cortical network, including premotor and temporo-parietal areas, has been proposed as the basis of the RHI. However, the causal contribution of these areas to the discrete illusory components remains unclear. We used transcranial direct current stimulation (tDCS) to assess the contribution of the right premotor cortex (rPMc) and the right temporo-parietal junction (rTPJ) to the RHI and explored the role of these areas in modulating the subjective experience of embodiment and the misperception of the hand position. We found that anodal tDCS of both rPMc and rTPJ increased the misjudgement of the real hand location towards the fake hand. Crucially, the difference in proprioceptive displacement evoked by the congruent and incongruent visuo-tactile stroking was minimised when tDCS was applied over the rPMc, while it was amplified when the rTPJ was targeted. The parietal effects of tDCS also extended to the self-report components of the RHI. These findings suggest that the tDCS of rTPJ modulates the RHI depending on the temporal congruency of the visuo-tactile stimulation, while the tDCS of rPMc induces a general recalibration of hand coordinates, regardless of the visuo-tactile congruency. The present results are discussed in the view of a multicomponent model of the RHI.

Experimentally induced limb-disownership in mixed reality

“…Our data suggest that transcranial stimulation affected the experience of ownership during both the illusion and control conditions, suggestive of a broad effect of stimulation that is not dependent on synchronous visuotactile feedback. This is in line with two recent neurostimulation studies reporting mainly non-illusion-specific effects of anodal stimulation over right PPC ( Convento et al, 2018;Lira et al, 2018).…”

“…In line with previous literature we expected stimulation of right parietal networks to modulate body ownership. This hypothesis is further supported by two recent tDCS studies reporting a modulation of the drift measure of the RHI in case of anodal stimulation applied over the right temporo-parietal junction (and right premotor cortex (Convento et al, 2018) and a change in the onset time of the illusion, but not drift, during anodal stimulation over right posterior parietal cortex (PPC) respectively (Lira et al, 2018). These studies further reported significant, if slightly different, effects of anodal tDCS on perceived body ownership.…”

“…Although these results may seem somewhat contradictory, they can be reconciled, if we assume the effect of stimulation in both the RHI and ReHI is relevant to inducing disownership over one's own limb. The underlying mechanism of this effect could on the one hand relate to a localized change in multisensory processing (Lira et al, 2018), body-specific integration (Convento et al, 2018;Tsakiris et al, 2008), or a re-weighting of sensory information over body-representation in the parietal lobe, or on the other hand a change in functionally connected regions such as the primary or secondary somatosensory cortex (Hänggi et al, 2017), where structural and functional hyper-connectivity have been reported in individuals with Xenomelia. This explanation is necessarily speculative but could further be investigated using neuroimaging alongside the ReHI paradigm.…”

Losing my hand. Body ownership attenuation after virtual lesion of the primary motor cortex

“…However, a recent study (Daltrozzo, Kotchoubey, Gueler, & Karim, ) showed an abnormal body perception (ABP) after inhibitory rTMS over rTPJ in 65% of their participants, but an ABP was reported also under inhibitory rTMS at the control site, supporting the idea that rTPJ may not play a specific role in this process. More recently, a different brain stimulation technique, such as transcranial direct current stimulation (tDCS), was used to assess the contribution of the right premotor cortex (rPMC) and the rTPJ to the RHI (Convento, Romano, Maravita, & Bolognini, ). In this study, the anodal tDCS on both rPMC and rTPJ increased the Proprioceptive Drift, even if the difference between synchronous and asynchronous condition was minimized when tDCS was applied over the rPMC, while it was amplified when the rTPJ was targeted.…”

Intermittent Theta Burst Stimulation Over Ventral Premotor Cortex or Inferior Parietal Lobule Does Not Enhance the Rubber Hand Illusion

“…Embodiment of a fake limb cannot be increased with non-invasive brain stimulation techniques due to a possible ceiling effect. However, the recent reports of a slight increase of proprioceptive drift and subjective experience of body ownership with transcranial direct current stimulation ( Convento et al, 2018 ; Lira et al, 2018 ) may suggest that iTBS could be not the better suited neuromodulating protocol for this purpose. iTBS was chosen because it is short and effective, but differences in the individual network sensitivity to the magnetic pulse ( Hamada et al, 2012 ) and in individual functional connectivity ( Nettekoven et al, 2015 ) make iTBS efficacy highly variable across subjects and, especially, across brain regions other than primary motor cortex ( Suppa et al, 2016 ).…”