Contributions of the Autonomic Nervous System to Brain Dynamics During Sleep and Wake

COEX 

It is well known that part of the fMRI signals variance is associated with fluctuations in systemic physiology, encompassing cardiac rate, respiration, and peripheral physiology. Recent research has revealed significant correlations between peripheral vascular tone, serving as a proxy for sympathetic activity, global fMRI signals, and autonomic arousals during light sleep. Additionally, investigations into the pulsatile movement and dynamics of cerebrospinal fluid (CSF) during sleep have unveiled its role in metabolic waste removal. These CSF pulsations may be induced by direct pressure effects from cardiac and respiratory cycles. For instance, deep inspirations altering intravascular CO2 can result in cerebral blood volume changes, inducing CSF pulsations through an autonomic pathway accompanied by variations in vascular tone during alert conditions. This pathway introduces a new dimension, illustrating the variability of sympathetic activity triggered by diverse stimuli, such as emotional and mental stress.
This educational talk will review recent findings emphasizing the potential to isolate respiratory-related fluctuations, such as CO2, from contributions of sympathetic activity to the fMRI signal. Furthermore, we will see how metrics like PPG amplitude and pupil diameter can serve as “autonomic regressors”, enhancing the interpretation of fMRI-based studies.