Dynamic BOLD functional connectivity in humans and its electrophysiological correlates

Area of Science:

• Neuroscience
• Cognitive Science
• Neuroimaging

Background:

• Neural oscillations are fundamental to human perception and cognition.
• Brain functional connectivity is dynamic, fluctuating with neural population synchronization.
• Dynamic functional connectivity is observable in spontaneous Blood Oxygen Level-Dependent (BOLD) signal fluctuations via functional Magnetic Resonance Imaging (fMRI).

Purpose of the Study:

• To investigate the electrophysiological correlates of dynamic BOLD functional connectivity.
• To analyze temporal fluctuations in BOLD connectivity using simultaneous electroencephalography (EEG) and fMRI.
• To examine how vigilance transitions affect these dynamic connectivity patterns.

Main Methods:

• Conducted long (≈50 min) simultaneous EEG and fMRI recordings in awake subjects and those undergoing vigilance transitions.
• Analyzed temporal fluctuations in BOLD connectivity across a network of 90 cortical and subcortical regions.
• Correlated EEG spectral power (alpha, beta, gamma bands) with fMRI BOLD connectivity and graph theoretical network indices.

Main Results:

• Increased alpha (8-12 Hz) and beta (15-30 Hz) power correlated with decreased BOLD functional connectivity.
• Increased gamma (30-60 Hz) power correlated positively with BOLD functional connectivity between specific brain regions.
• Vigilance transitions altered these patterns, with slower oscillations correlating with increased functional connectivity; alpha power changes related to network average path length.

Conclusions:

• Fluctuations in BOLD functional connectivity have a demonstrable neurophysiological basis.
• Gamma power increases may facilitate BOLD connectivity for cognitive integration.
• Alpha power decreases suggest temporary weakening of connectivity associated with idling states.