Large-Scale Brain Networks Related To Social Working Memory And Empathy

Humans possess unique social cognitive abilities that set us apart from other species. These abilities may be partially supported by another crucial capacity for maintaining and manipulating social information, such as people’s concerns,traits,and mental states. Therefore, efficient social working memory (WM) is essential to successful social interactions. Numerous evidences indicate that cognition and behavior is not caused by the activation of isolated brain regions, but by the dynamic interaction between multiple large-scale brain networks. The technical of functional networks connectivity is one of the main strategies and methods to reflect the brain functional integration. Functional connectivity networks are known to be sensitive to cognitive state, as the strength of connectivity is altered during task engagement relative to the resting state.Some recent findings indicate that not only is the network structure of the brain altered during task performance, but also that such alterations persist after the task ends. However, whether the connectivity alterations induced by social working memory have this persist effect, and the direction of this effect remain unknown.Previous WM studies using the n-back paradigm consistently reported activation in the frontoparietal control network (FPC). Recently, increasing evidence has highlighted the role of the FPC in cognitive control. The top-down control function of the FPC allows for focusing attention on goal-relevant information and suppressing goal-irrelevant information. In contrast to the FPC, the activity of the default mode network (DMN) has been documented as typically diminishing during performing WM. The DMN is thought to support internally-oriented and self-referential mental processes, such as mind-wandering, autobiographical memory retrieval, imagining the future, and theory of mind. Therefore, DMN activity may produce internal interference which interrupts externally-oriented attention tasks. The deactivation of the DMN serves to suppress irrelevant thoughts and focus more attention on the task. The FPC and DMN operate in a competitive or antagonistic relationship during tasks requiring externally-directed attention.A recent study indicated that the top-down signals from the FPC suppressed the internal noise from the DMN to improve externally-oriented task performance.However, this proposed anti-correlation between the FPC and DMN needs to be further ascertained in social WM. because some recent findings suggest that social WM and classical WM may rely on different neural mechanisms. Furthermore, the FPC was found anatomically situated between components of the DMN and the dorsal attention network (DAN), providing a spatial convenience to reallocate cognitive resources from different systems. The FPC plays a pivotal gate-keeping role in goal-directed cognition, modulating the dynamic balance between the DMN and DAN. However, the modulatory role played by the FPC has rarely been investigated in previous studies related to social WM. In this study, we aimed to fill this gap by exploring the functional connectivity of the FPC-DMN and FPC-DAN during social WM task performance.Empathy is an ability to understand and share the mental states of others, and it is crucial to human emotional experiences and social interactions. As the core of advanced cognitive processes of humans,WM definitely is important to empathy processing. Moreover, some recent studies found higher emotional empathy contributed to emotional recognition WM. These findings suggest that there may be an association between empathy and social WM.Although to date there has been a great deal of research regarding the neural bases of empathy, they mostly focused on some specific brain regions, and rarely explored from the level of functional connectivity between large-scale networks.A large body of evidence has suggested that the DMN plays an important role in empathy, and some core regions in the FPC have also been reported to be involved in empathy. Based on these results, we speculated that empathy might be associated with FPC-DMN connectivity, and individuals with higher empathic ability would perform better in social WM tasks.To investigate these questions, we measured FPC-DMN connectivity during resting state and two emotional face recognition WM tasks using the 2-back paradigm.Thirty-four individuals were instructed to perform the tasks based on either the expression [emotion (EMO)] or the identity (ID) of the same set of face stimuli.In the first study, we firstly investigated the modulation on large-scale brain network by social WM load. Consistent with previous studies, an increased anti-correlation between the FPC and DMN was observed during both tasks relative to the resting state. Specifically, this anti-correlation during the EMO task was stronger than during the ID task, as the former has a higher social load. What’s more, in the FPC and DMN, there were significant task-related differences in percent signal changes relative to the resting state. Secondly, we analyzed the association between self-reported empathy and social WM performance. Intriguingly, the subjects with higher empathy scores exhibited better social WM performance in EMO task. Moreover, individual differences in empathy were significantly correlated with the FPC-DMN anti-correlation in the EMO task. These results indicate that the top-down signals from the FPC suppress the DMN to support social WM and empathy. In the second study, by comparing the DMN-FPC and DMN-DAN connectivity during an initial rest period acquired upon entering the scanner, a second rest period following execution of the EMO task, and a third rest period following execution of the ID task, we aimed to investigate the prior brain state, as determined by the activity engaged in immediately prior to collection of resting state data, can influence the networks recovered by resting state functional connectivity (rFC) analyses. We found that the DMN-FPC and DMN-DAN anti-correlation became weaker both during the resting states after the EMO task and the ID task relative to the initial rest period. This result indicates that not all resting states are equivalent, that is, prior cognitive state can influence subsequent rFC.