Simultaneous EEG and fMRI of the alpha rhythm

TLDR

The alpha rhythm in the EEG is 8–12 Hz activity present when a subject is awake with eyes closed. The study used simultaneous EEG and fMRI to map brain regions whose MRI signal reliably changed with posterior alpha activity modulation. Eleven subjects were scanned while resting with eyes closed, using simultaneous EEG and fMRI to record alpha activity and corresponding BOLD signals. Increased alpha power correlated with decreased MRI signal in occipital, superior temporal, inferior frontal, and cingulate cortex, and with increased signal in thalamus and insula, supporting the view that the alpha rhythm indexes cortical inactivity partly generated by the thalamus and highlighting implications for interpreting resting baseline in fMRI.

Abstract

The alpha rhythm in the EEG is 8–12 Hz activity present when a subject is awake with eyes closed. In this study, we used simultaneous EEG and fMRI to make maps of regions whose MRI signal changed reliably with modulation in posterior alpha activity. We scanned 11 subjects as they rested with eyes closed. We found that increased alpha power was correlated with decreased MRI signal in multiple regions of occipital, superior temporal, inferior frontal, and cingulate cortex, and with increased signal in the thalamus and insula. These results are consistent with animal experiments and point to the alpha rhythm as an index of cortical inactivity that may be generated in part by the thalamus. These results also may have important implications for interpretation of resting baseline in fMRI studies.