No Change in Social Decision-Making Following Transcranial Direct Current Stimulation of the Right Temporoparietal Junction.

Laura F. Blair-West,Paul B. Fitzgerald,Phillip J. Hall,Kate E. Hoy,Bernadette M. Fitzgibbon

doi:10.3389/fnins.2018.00258

Abstract

The right temporoparietal junction (rTPJ) is thought to play an important role in social cognition and pro-social decision-making. One way to explore this link is through the use of transcranial direct current stimulation (tDCS), a non-invasive brain stimulation method that is able to modulate cortical activity. The aim of this research was therefore to determine whether anodal tDCS to the rTPJ altered response to a social decision-making task. In this study, 34 healthy volunteers participated in a single-center, double-blinded, sham-controlled crossover design. Subjects received 20 min of active/sham anodal tDCS to the rTPJ before undertaking the Ultimatum Game (UG), a neuroeconomics paradigm in which participants are forced to choose between monetary reward and punishing an opponent's unfairness. Contrary to expectations, we found no significant difference between anodal and sham stimulation with regard to either the total number or reaction time of unfair offer rejections in the UG. This study draws attention to methodological issues in tDCS studies of the rTPJ, and highlights the complexity of social decision-making in the UG.

Highlights

The right temporoparietal junction is a region of increasing interest in studies of the social brain
Bayesian analyses were used to compare active and sham groups regarding the total number (BF01 = 3.566, error = 1.031e-6) and response reaction time (BF01 = 4.121, error = 0.035) data, confirming that the findings most likely represented a null effect from stimulation
The present study investigated the effects of anodal transcranial direct current stimulation (tDCS) to the right temporoparietal junction (rTPJ) on social decision-making

Summary

Introduction

The right temporoparietal junction (rTPJ) is a region of increasing interest in studies of the social brain. It encompasses the supramarginal gyrus, caudal parts of the superior temporal gyrus, and dorsal-rostral parts of the occipital gyrus, and is reciprocally connected to the right prefrontal cortex and temporal lobe (Decety and Lamm, 2007). The rTPJ is thought to be involved in the mentalizing process, in which one discerns the mental states of other humans (Frith and Frith, 2006). Through its role in empathy processing, rTPJ function may encourage pro-social tDCS to rTPJ: Social Decision-Making behavior, and to date functional brain imaging techniques have provided partial evidence for this claim. Increased gray matter volume of the rTPJ is linked with altruism (Morishima et al, 2012), and rTPJ activity is heightened during pro-social decision-making (Zanon et al, 2014)

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