EEG K-complexes during sleep are followed by significant drops in finger skin vascular tone and widespread fMRI signal decreases in gray matter (z = -0.33, p < 0.01), indicating a sympathetic contribution to the fMRI signal.
Observational (n=11)
Sympathetic nervous system activity, as indexed by EEG K-complexes and peripheral vascular tone drops, significantly contributes to the global fMRI signal, highlighting the need to account for systemic vascular effects in neuroimaging.
Effect estimate: z = -0.33
p-value: p=<0.01
The interpretation of functional magnetic resonance imaging (fMRI) studies of brain activity is often hampered by the presence of brain-wide signal variations that may arise from a variety of neuronal and non-neuronal sources. Recent work suggests a contribution from the sympathetic vascular innervation, which may affect the fMRI signal through its putative and poorly understood role in cerebral blood flow (CBF) regulation. By analyzing fMRI and (electro-) physiological signals concurrently acquired during sleep, we found that widespread fMRI signal changes often co-occur with electroencephalography (EEG) K-complexes, signatures of sub-cortical arousal, and episodic drops in finger skin vascular tone; phenomena that have been associated with intermittent sympathetic activity. These findings support the notion that the extrinsic sympathetic innervation of the cerebral vasculature contributes to CBF regulation and the fMRI signal. Accounting for this mechanism could help separate systemic from local signal contributions and improve interpretation of fMRI studies.
Özbay et al. (Mon,) conducted a observational in Healthy (Sleep Study) (n=11). EEG K-complexes (sub-cortical arousal) vs. Absence of K-complexes was evaluated on Correlation between low-frequency EEG increases (K-complexes) and fMRI signal decrease in gray matter (z = -0.33, p=<0.01). EEG K-complexes during sleep are followed by significant drops in finger skin vascular tone and widespread fMRI signal decreases in gray matter (z = -0.33, p < 0.01), indicating a sympathetic contribution to the fMRI signal.