Sympathetic activity contributes to the fMRI signal

Area of Science:

• Neuroimaging
• Neurophysiology
• Autonomic Nervous System

Background:

• Functional magnetic resonance imaging (fMRI) interpretation is challenged by widespread brain signal variations from diverse sources.
• The sympathetic vascular innervation's role in regulating cerebral blood flow (CBF) and its impact on fMRI signals is poorly understood.

Purpose of the Study:

• To investigate the relationship between sympathetic activity, CBF regulation, and fMRI signal variations during sleep.
• To determine if sympathetic innervation contributes to systemic fMRI signal changes.

Main Methods:

• Concurrent acquisition of fMRI and electrophysiological (EEG) signals during sleep.
• Analysis of fMRI signal changes in conjunction with EEG K-complexes and finger skin vascular tone.

Main Results:

• Widespread fMRI signal changes during sleep frequently co-occurred with EEG K-complexes, indicating sub-cortical arousal.
• These fMRI changes were associated with intermittent drops in finger skin vascular tone, linked to sympathetic activity.

Conclusions:

• Findings support the contribution of extrinsic sympathetic innervation to cerebral blood flow regulation and fMRI signals.
• Accounting for sympathetic influence may help differentiate systemic from local fMRI signal sources, enhancing study interpretation.