Why I tense up when you watch me: Inferior parietal cortex mediates an audience's influence on motor performance.

Michiko Yoshie,Neil A Harrison,Hugo D Critchley,Yoko Nagai

doi:10.1038/srep19305

Abstract

The presence of an evaluative audience can alter skilled motor performance through changes in force output. To investigate how this is mediated within the brain, we emulated real-time social monitoring of participants’ performance of a fine grip task during functional magnetic resonance neuroimaging. We observed an increase in force output during social evaluation that was accompanied by focal reductions in activity within bilateral inferior parietal cortex. Moreover, deactivation of the left inferior parietal cortex predicted both inter- and intra-individual differences in socially-induced change in grip force. Social evaluation also enhanced activation within the posterior superior temporal sulcus, which conveys visual information about others’ actions to the inferior parietal cortex. Interestingly, functional connectivity between these two regions was attenuated by social evaluation. Our data suggest that social evaluation can vary force output through the altered engagement of inferior parietal cortex; a region implicated in sensorimotor integration necessary for object manipulation, and a component of the action-observation network which integrates and facilitates performance of observed actions. Social-evaluative situations may induce high-level representational incoherence between one’s own intentioned action and the perceived intention of others which, by uncoupling the dynamics of sensorimotor facilitation, could ultimately perturbe motor output.

Highlights

To address this, we devised a simple motor task, which was an adaption of earlier pinch- and power-grip tasks[11,12,13,14] and was designed to capture subtle changes in tonic muscle tension evoked by the presence of an evaluative audience (Fig. 1)
Social evaluation led to the attenuation of this force decay, or the relative increase in grip force during the 10% maximal voluntary contraction (MVC) task
The results are consistent with a previous study showing that the presentation of emotional images attenuated force decay in a similar feedback-occluded isometric grip task at 10% MVC11

Summary

Introduction

When the presence of evaluative observers influences our motor behaviour, visual information relating to the feelings and intentions of these individuals (e.g., facial expressions, direction of gaze) first needs to be processed in the brain Previous studies both in monkeys and humans have identified the posterior superior temporal sulcus (pSTS) as a key neural substrate for social perception based on visual cues[15,16,17]. Given our use of a similar isometric grip task, we hypothesised that effects of social evaluation on motor performance would be mediated via actions on the IPC Supporting this prediction, during social observation processing of social features within the pSTS region is known to be conveyed to the IPC, which is capable of generating appropriate motor actions based on the social cues[20]. We investigated whether activity within the IPC is modulated in relation to the inter- and intra-individual variability in the effects of social evaluation on force output

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Conclusion