Interbrain synchrony and its potential role in modulating the impact of traumatic events.

Exposure to traumatic events has far-reaching effects on mental health. While social factors are known to exert buffering effects on trauma exposure, the underlying neural mechanisms that mediate these effects remain largely unexplored. Since interbrain synchrony is associated with social connectedness, we investigate whether individuals exhibiting a higher tendency for interbrain synchrony demonstrate reduced trauma-related symptoms. To examine whether interbrain synchrony assessed before trauma exposure moderated response to traumatic events, 98 participants who had previously participated in a hyperscanning functional near-infrared spectroscopy (fNIRS) study, which measured interbrain synchrony during an initial interaction with a stranger, were contacted following the terrorist attack in Israel on October 7th, 2023. They completed a questionnaire assessing their level of trauma exposure during the attack. As expected, the level of exposure to traumatic events was positively associated with PTSD, depression, and general psychiatric symptoms. As hypothesized, this association was moderated by interbrain synchrony, such that the greater the interbrain synchronization of brain activity in multiple brain regions, the weaker the association between exposure to traumatic events and symptoms reported by these individuals. This effect was most prominent in the left pre-motor cortex, which is part of the observation-execution system. These findings suggest that increased spontaneous interbrain synchronization during free conversations serves as a marker of social adaptation to the adversities of trauma and moderates the effects of traumatic exposure. Considering that interbrain synchrony facilitates social connection, these findings hold that individuals with a stronger predisposition for social connection are better equipped to cope with trauma.