Multimodal EEG-HRV assessment of individual regulatory patterns: a perturbation-based approach toward precision psychiatry.

BACKGROUND: Contemporary psychiatric research increasingly emphasizes the need for objective, biologically grounded markers to complement symptom-based diagnostic frameworks. While electroencephalography (EEG) has been widely used to investigate neural dynamics associated with attention, arousal, and cognitive control, these approaches are typically brain-centric and rely on static or resting-state paradigms. Integration of autonomic dynamics remains limited despite theoretical models highlighting brain-body interactions. METHODS: In the present pilot study, we employed a multimodal, perturbation-based paradigm combining wearable EEG and heart rate variability (HRV) to examine cortico-autonomic regulatory dynamics. Ten healthy participants were exposed to brief auditory conditions (silence, noise-based stimulation, and binaural-beat auditory input). Frontal upper-beta activity (β2; 21-30 Hz) and vagally mediated HRV indices (RMSSD, HF power) were analyzed to characterize within-subject regulatory responses across conditions. RESULTS: Condition-related variation was observed descriptively in both cortical and autonomic measures, although no statistically significant group-level effects were detected. Substantial inter-individual variability emerged in the direction and magnitude of these responses. Notably, substantial inter-individual variability emerged in both the direction and magnitude of physiological responses. In several participants, coordinated changes between EEG and HRV measures suggested multimodal cortico-autonomic response patterns, whereas others exhibited divergent or minimal response profiles. Coordinated decreases in frontal β2 activity together with increases in RMSSD were observed in 4 of the 10 participants. Given the exploratory nature of the study and the limited sample size, these observations should be interpreted as preliminary and hypothesis-generating. CONCLUSION: These findings support the potential utility of multimodal, stimulus-dependent approaches for characterizing dynamic brain-body responses beyond static biomarkers. The observed multimodal response configurations are consistent with coordinated cortico-autonomic response patterns and provide a useful framework for generating hypotheses regarding individual variability in brain-body regulation. As an exploratory pilot study, the present findings require validation in larger and clinically diverse cohorts before conclusions regarding physiological subgroups or clinical applications can be drawn. This perturbation-based multimodal EEG-HRV framework may contribute to future physiology-informed precision psychiatry research by providing a methodological foundation for characterizing individual brain-body response variability.