Research ReportThe contribution of different frequency bands of fMRI data to the correlation with EEG alpha rhythm

- Various BOLD frequency bands contribute differently to fMRI/EEG correlation analyses.
- Different networks influence the alpha rhythm in different frequencies.
- The EEG-BOLD correlations concentrate in relatively narrow frequency bands.

Alpha rhythm is a prominent EEG rhythm observed during resting state and is thought to be related to multiple cognitive processes. Previous simultaneous electroencephalography (EEG)/functional magnetic resonance imaging (fMRI) studies have demonstrated that alpha rhythm is associated with blood oxygen level dependent (BOLD) signals in several different functional networks. How these networks influence alpha rhythm respectively is unclear. The low-frequency oscillations (LFO) in spontaneous BOLD activity are thought to contribute to the local correlations in resting state. Recent studies suggested that either LFO or other components of fMRI can be further divided into sub-components on different frequency bands. We hypothesized that those BOLD sub-components characterized the contributions of different brain networks to alpha rhythm. To test this hypothesis, EEG and fMRI data were simultaneously recorded from 17 human subjects performing an eyes-close resting state experiment. EEG alpha rhythm was correlated with the filtered fMRI time courses at different frequency bands (0.01-0.08 Hz, 0.08-0.25 Hz, 0.01-0.027 Hz, 0.027-0.073 Hz, 0.073-0.198 Hz, and 0.198-0.25 Hz). The results demonstrated significant relations between alpha rhythm and the BOLD signals in the visual network and in the attention network at LFO band, especially at the very low frequency band (0.01-0.027 Hz).