BOLD correlates of EEG alpha phase-locking and the fMRI default mode network

Area of Science:

• Neuroscience
• Brain Imaging
• Electrophysiology

Background:

• Brain area synchronization is crucial for information processing.
• Electroencephalography (EEG) studies have extensively investigated synchronous brain oscillations, particularly alpha-band activity.
• Functional magnetic resonance imaging (fMRI) reveals synchronous BOLD (blood-oxygen-level-dependent) signal oscillations forming resting-state networks (RSNs).

Purpose of the Study:

• To investigate the relationship between EEG synchronization and fMRI BOLD signal within RSNs.
• To test the hypothesis that specific RSNs are organized by EEG rhythms.
• To explore the spatio-temporal organization of brain activity.

Main Methods:

• Simultaneous EEG/fMRI recordings were used.
• Global EEG synchronization (GFS) in the alpha frequency band was analyzed.
• BOLD signal correlates of GFS were identified and mapped to RSNs.

Main Results:

• BOLD correlates of alpha-band GFS were found in brain areas belonging to specific RSNs, such as the default mode network.
• Results support the hypothesis that RSNs are organized by long-range synchronization in the alpha band.
• Specific overlapping regions between GFS BOLD correlates and RSNs were localized.

Conclusions:

• Brain activity organization involves not only spectral dynamics but also spatio-temporal synchronization.
• Alpha-band EEG synchronization plays a role in organizing large-scale brain networks.
• This study provides evidence for the coordination of RSNs by EEG rhythms.