Body and brain responses to acute psychosocial stress: physiological markers during the Trier Social Stress Test (TSST).

Acute psychosocial stress elicits coordinated changes across central neural activity and peripheral autonomic physiology, yet many studies focus on isolated time points or single physiological systems. This limits understanding of stress as a dynamic brain–body process unfolding across anticipation, exposure, and recovery. The present thesis investigates phase-specific neural and autonomic responses to acute psychosocial stress using the Trier Social Stress Test (TSST), integrating electroencephalography (EEG), electrocardiography (ECG), and electrodermal activity (EDA) within a multimodal framework. High-density EEG recordings were obtained alongside autonomic measures in healthy adults across four TSST phases: baseline, anticipation, speech (acute stress), and recovery. Oscillatory EEG activity was quantified using power spectral density in the delta, theta, alpha, and beta frequency bands across predefined scalp clusters. Autonomic reactivity was assessed using heart rate, heart rate variability indices, skin conductance level, and phasic skin conductance responses, while subjective stress was measured using state anxiety ratings. Phase-dependent effects and spatial patterns were examined using linear mixed-effects models accounting for repeated measurements, followed by post-hoc contrasts. Associations between neural and autonomic changes were explored using correlational analyses. Results revealed robust phase-specific modulation of both neural and autonomic measures. Delta, theta, and beta power increased during acute stress relative to baseline, while alpha power showed a distinct phase-dependent pattern consistent with increased cortical engagement during stress exposure. Autonomic indices confirmed successful stress induction, with elevated sympathetic arousal during the speech phase and gradual recovery thereafter. Importantly, individual differences in neural activity during the speech phase were associated with stress reactivity: lower delta and alpha power were related to stronger sympathetic activation and higher subjective anxiety, whereas increases in beta power were associated with greater autonomic reactivity. Together, these findings demonstrate that acute psychosocial stress is characterized by coordinated, phase-dependent brain–body dynamics, and that individual differences in neural oscillatory patterns—particularly within delta, alpha, and beta bands—relate meaningfully to autonomic and subjective stress responses. By integrating EEG and autonomic measures, this thesis highlights the value of multimodal approaches for understanding stress regulation and individual variability within an interoceptive and predictive framework.