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Introduction Cerebrospinal fluid (CSF) pulsations are linked to hemodynamics, with autonomic mechanisms, suggested to modulate slow-wave induced pulsations. Method To explore autonomic regulation’s role in neurofluid flow, independent of sleep and neural activity, we hypothesized that modulating basal CO 2 (altering vascular tone, cardiac activity and respiration) would highlight this link. Results Using resting-state BOLD fMRI in neurofluid regions under different CO 2 levels (capnic states), we found: 1) biomechanical modulation does not explain neurofluid dynamic variations across capnias; 2) beyond respiration, heart-rate variability independently drives low-frequency neurofluid flow, indicating autonomic control; 3) altered CO 2 primarily affects neurofluid dynamics through the frequency (and not amplitude) of heart-rate and respiratory-volume variability. Discussion These results suggest that both hyper- and hypocapnia disrupt how CSF responds to autonomic regulation, seen in deviations from normal cardiac and respiratory responses. Our work reveals neurofluid dynamics’ sensitivity to CO 2 ’s frequency response, best explained by autonomic modulation. Modulating basal CO 2 offers a new way to influence human neurofluid dynamics, independent of sleep or neuronal activity.
Zhong et al. (Wed,) studied this question.