Alcohol and the Social Brain: An Alcohol-Administration Hyperscanning Study Employing a Within-Subject Design

Objective:

Alcohol's ability to enhance social bonding and modulate mood in social contexts has been identified as a key factor contributing to its reinforcing properties and risk for Alcohol Use Disorder (AUD). While prior research has demonstrated alcohol's role in enhancing social interactions, laboratory studies often fail to replicate the real-world context in which most alcohol consumption occurs-social settings with familiar companions. This discrepancy limits our understanding of the mechanisms through which alcohol exerts its effects in social contexts.

This study is the first to employ EEG hyperscanning methods to investigate the inter- and intra-brain mechanisms underlying alcohol's social rewards within dyadic interactions. Specifically, the study aims to characterize how alcohol modulates social bonding, emotional regulation, and neural synchrony during social interactions, and to identify the cognitive and affective processes driving alcohol's reinforcing properties. The findings are expected to deepen understanding of the role of alcohol in social dynamics and inform interventions for AUD.

Study Population:

The study will recruit 200 participants, aged 21-30, who self-identify as regular social drinkers and with no reported history of severe alcohol use disorder.

Design:

This within-subject laboratory study involves two experimental sessions spaced approximately one week apart. Each session includes participants interacting in dyads with a stranger, where they will consume either a moderate dose of alcohol (target BAC \~0.08%) or a non-alcoholic control beverage, with the order randomized between sessions. Participants will engage in structured and unstructured tasks during each session, allowing for the evaluation of behavioral, emotional, and neural outcomes in both intoxicated and sober states.

* EEG Hyperscanning: Neural activity will be recorded simultaneously from both members of the dyad using EEG hyperscanning technology. This allows for the investigation of intra-brain processes (e.g., cognitive and emotional regulation) and inter-brain synchrony (e.g., neural alignment during social interactions). * Tasks and Measures: Participants will complete tasks designed to assess social bonding, emotional regulation, and cognitive processing. Tasks include structured paradigms (e.g., music perception tasks and flanker task) and naturalistic social interactions. These are complemented by self-report measures assessing mood, social closeness, and perceptions of the interaction. * Randomization and Counterbalancing: The order of alcohol versus control sessions will be randomized across participants to control for carryover effects.

Outcome Measures:

1. Neurophysiological Outcomes:

Intra and Inter Brain Coupling (IBC): * Intra brain synchrony (within-subject): Coherence or phase-locking between brain regions within the same participant, compared across sober versus intoxicated states. * Inter brain synchrony (between-subject): Synchronization metrics (e.g., inter subject PLV, inter subject correlation) between paired participants, assessed separately in sober and intoxicated conditions

Event Related Potentials (ERP):

• Amplitudes and latencies of task-related ERP components, specifically Feedback Related Negativity (FRN), measured both for the operating ("player") and observing ("observer") participant, with comparisons across sobriety conditions 2. Behavioral and Psychological Outcomes:

Self-reported mood and social bonding assessed pre- and post-interaction using validated measures such as the Inclusion of Other in Self Scale and the Biphasic Alcohol Effects Scale.

Observational coding of nonverbal behaviors (e.g., facial expressions, body language) during dyadic interactions. 3. Drinking Behavior:

Longitudinal self-reports of drinking patterns and alcohol-related outcomes.