Dynamic fluctuations in ascending heart–to–brain modulations under mental stress elicitation

Dynamical information exchange between central and autonomous nervous systems, as referred to functional brain–heart interplay, occurs during emotional and physical arousal. Nevertheless, the role of such a nervous-system-wise communication in mental stress is yet unknown. In this study, we estimate the causal and bidirectional neural modulations between EEG oscillations and peripheral sympathetic and parasympathetic activities using a recently proposed computational framework for a functional brain–heart interplay assessment, namely the sympatho-vagal synthetic data generation model. Mental stress is elicited in 37 healthy volunteers by increasing their cognitive demand throughout four tasks associated with increasing stress levels. Stress elicitation induced an increased variability in the directional heart–to–brain functional interplay, primarily originating from sympathetic activity targeting a wide range of EEG oscillations. These findings extend current knowledge on stress physiology, which referred to primarily a top-down neural dynamics. Our results suggest that mental stress involves dynamic and bidirectional neural interactions at a brain–body level, where bodily feedback may modulate the perceived stress caused by an increased cognitive demand. We conclude that directional brain–heart interplay measurements may provide suitable biomarkers for a quantitative stress assessment.