Abstract
During joint action, two or more persons depend on each other to accomplish a goal. This mutual recursion, or circular dependency, is one of the characteristics of cooperation. To evaluate the neural substrates of cooperation, we conducted a hyperscanning functional MRI study in which 19 dyads performed a joint force-production task. The goal of the task was to match their average grip forces to the target value (20% of their maximum grip forces) through visual feedback over a 30-s period; the task required taking into account other-produced force to regulate the self-generated one in real time, which represented cooperation. Time-series data of the dyad's exerted grip forces were recorded, and the noise contribution ratio (NCR), a measure of influence from the partner, was computed using a multivariate autoregressive model to identify the degree to which each participant's grip force was explained by that of their partner's, i.e., the degree of cooperation. Compared with the single force-production task, the joint task enhanced the NCR and activated the mentalizing system, including the medial prefrontal cortex, precuneus, and bilateral posterior subdivision of the temporoparietal junction (TPJ). In addition, specific activation of the anterior subdivision of the right TPJ significantly and positively correlated with the NCR across participants during the joint task. The effective connectivity of the anterior to posterior TPJ was upregulated when participants coordinated their grip forces. Finally, the joint task enhanced cross-brain functional connectivity of the right anterior TPJ, indicating shared attention toward the temporal patterns of the motor output of the partner. Since the posterior TPJ is part of the mentalizing system for tracking the intention of perceived agents, our findings indicate that cooperation, i.e., the degree of adjustment of individual motor output depending on that of the partner, is mediated by the interconnected subdivisions of the right TPJ.
Highlights
Cooperation is a type of human interaction in which two or more individuals coordinate their behavior to pursue a common goal (Bratman, 1992)
Since the posterior temporoparietal junction (TPJ) is part of the mentalizing system for tracking the intention of perceived agents, our findings indicate that cooperation, i.e., the degree of adjustment of individual motor output depending on that of the partner, is mediated by the interconnected subdivisions of the right TPJ
Task errors in the PS and PJ conditions were evaluated by the root-mean-square error (RMSE)
Summary
Cooperation is a type of human interaction in which two or more individuals coordinate their behavior to pursue a common goal (Bratman, 1992). Several studies have attempted to identify the brain regions involved in cooperation by using simultaneous joint coordination tasks (Chaminade et al, 2012; Newman-Norlund et al, 2008). Newman-Norlund et al (2008) compared the neural substrates of Abbreviations: 3-D, three-dimentional; ACC, anterior cingulate cortex; AG, angular gyrus; ALE, activation likelihood estimation; ANOVA, analysis of variance; dmPFC, dorsomedial prefrontal cortex; fMRI, functional magnetic resonance; FWE, family-wise error; GLM, general linear model; IFG, inferior frontal gyrus; MFPG, medial frontopolar gyrus; MNS, mirror neuron system; PJ, perform-joint; PS, perform-single; RMSE, root-mean-square error; ROI, region of interest; SFG, superior frontal gyrus; SMG, supramarginal gyrus; STG, superior temporal gyrus; TE, echo time; TPJ, temporoparietal junction; TPJa, anterior TPJ; TPJp, posterior TPJ; TR, repetition time; vmPFC, ventromedial PFC; WJ, watch-joint; WS, watch-single; NCR, noise contribution ratio
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