Intra- and inter-brain synchrony oscillations underlying social adjustment

Abstract

Humans naturally synchronize their behavior with other people. However, although it happens almost automatically, adjusting behavior and conformity to others is a complex phenomenon whose neural mechanisms are still yet to be understood entirely. The present experiment aimed to study the oscillatory synchronization mechanisms underlying automatic dyadic convergence in an EEG hyperscanning experiment. Thirty-six people performed a cooperative decision-making task where dyads had to guess the correct position of a point on a line. A reinforcement learning algorithm was used to model different aspects of the participants' behavior and their expectations of their peers. Intra- and inter-connectivity among electrode sites were assessed using inter-site phase clustering in three main frequency bands (theta, alpha, beta) using a two-level Bayesian mixed-effects modeling approach. The results showed two oscillatory synchronization dynamics related to attention and executive functions in alpha and reinforcement learning in theta. In addition, inter-brain synchrony was mainly driven by beta oscillations. This study contributes preliminary evidence on the phase-coherence mechanism underlying inter-personal behavioral adjustment.

Figure 1

Intra-brain coherence connection maps in the alpha frequency range in the first (0–500 ms, top) and second (500–1000 ms, bottom) time ranges in the first adjustment (FB2–FB1). Color and size of each electrode sites indicate the number of credible connections with other electrodes, and the maximum and minimum are specific to each representation.

Figure 2

Inter-brain coherence connection maps in the beta frequency range (first time-range, 0–500 ms., top) and alpha (second time-range, 500–1000 ms., bottom) bands in the first adjustment (FB2-FB1).

Figure 3

Intra-brain coherence connection maps showing an enhanced synchronization in theta band in the first phase (0–500 ms) of the second adjustment (FB3–FB2) for PEs (top) for Models 1 and 3. Color and size indicate the number of credible connections with other electrode sites, and the maximum and minimum are specific to each representation.

Figure 4

Diagram of experimental paradigm, which consists of two phases: the “pre-task” (first part, 1) and the main task with dual EEG recording (second part, 2). Below there is a representation of the room setting in these two phases. Participants (Part. 1 and Part. 2) shared the room in both phases, but a separator was added in the second phase to prevent communication. In the main task, every trial starts with an informative trial number (A), followed by a fixation cross for 500 ms (B), the stimulus participants used for their estimations (C) which is the moment when they had to use their keypads to introduce their responses, another fixation cross for 500 ms (D) and, finally, the feedback (E). Steps from B to E were repeated 3 consecutive times.