An Active-Inference Approach to Second-Person Neuroscience

Neural mechanisms underlying the interactive exchange of facial emotional expressions

Facial emotional expressions are crucial in face-to-face social interactions, and recent findings have highlighted their interactive nature. However, the underlying neural mechanisms remain unclear. This electroencephalography study investigated whether the interactive exchange of facial expressions modulates socio-emotional processing. Participants (N = 41) displayed a facial emotional expression (angry, neutral, or happy) toward a virtual agent, and the agent then responded with a further emotional expression (angry or happy) or remained neutral (control condition). We assessed subjective experience (valence, arousal), facial EMG (Zygomaticus, Corrugator), and event-related potentials (EPN, LPP) elicited by the agent's response. Replicating previous findings, we found that an agent's happy facial expression was experienced as more pleasant and elicited increased Zygomaticus activity when participants had initiated the interaction with a happy compared to an angry expression. At the neural level, angry expressions resulted in a greater LPP than happy expressions, but only when participants directed an angry or happy, but not a neutral, expression at the agent. These findings suggest that sending an emotional expression increases salience and enhances the processing of received emotional expressions, indicating that an interactive setting alters brain responses to social stimuli.

Inter-brain desynchronization in social interaction: a consequence of subjective involvement?

Hyperscanning approaches to human neuroscience aim to uncover the neural mechanisms of social interaction. They have been largely guided by the expectation that increased levels of engagement between two persons will be supported by higher levels of inter-brain synchrony (IBS). A common approach to measuring IBS is phase synchrony in the context of EEG hyperscanning. Yet the growing number of experimental findings does not yield a straightforward interpretation, which has prompted critical reflections about the field's theoretical and methodological principles. In this perspective piece, we make a conceptual contribution to this debate by considering the role of a possibly overlooked effect of inter-brain desynchronization (IBD), as for example measured by decreased phase synchrony. A principled reason to expect this role comes from the recent proposal of irruption theory, which operationalizes the efficacy of a person's subjective involvement in behavior generation in terms of increased neural entropy. Accordingly, IBD is predicted to increase with one or more participant's socially motivated subjective involvement in interaction, because of the associated increase in their neural entropy. Additionally, the relative prominence of IBD compared to IBS is expected to vary in time, as well as across frequency bands, depending on the extent that subjective involvement is elicited by the task and/or desired by the person. If irruption theory is on the right track, it could thereby help to explain the notable variability of IBS in social interaction in terms of a countertendency from another factor: IBD due to subjective involvement.

A dual-brain therapeutic approach using noninvasive brain stimulation based on two-person neuroscience: A perspective review

Our actions and decisions in everyday life are heavily influenced by social interactions, which are dynamic feedback loops involving actions, reactions, and internal cognitive processes between individual agents. Social interactions induce interpersonal synchrony, which occurs at different biobehavioral levels and comprises behavioral, physiological, and neurological activities. Hyperscanning-a neuroimaging technique that simultaneously measures the activity of multiple brain regions-has provided a powerful second-person neuroscience tool for investigating the phase alignment of neural processes during interactive social behavior. Neural synchronization, revealed by hyperscanning, is a phenomenon called inter-brain synchrony- a process that purportedly facilitates social interactions by prompting appropriate anticipation of and responses to each other's social behaviors during ongoing shared interactions. In this review, I explored the therapeutic dual-brain approach using noninvasive brain stimulation to target inter-brain synchrony based on second-person neuroscience to modulate social interaction. Artificially inducing synchrony between the brains is a potential adjunct technique to physiotherapy, psychotherapy, and pain treatment- which are strongly influenced by the social interaction between the therapist and patient. Dual-brain approaches to personalize stimulation parameters must consider temporal, spatial, and oscillatory factors. Multiple data fusion analysis, the assessment of inter-brain plasticity, a closed-loop system, and a brain-to-brain interface can support personalized stimulation.