Neurophysiologic tools are complementary to fMRI for examining brain network activity. Electroencephalographic (EEG) signals oscillate on a faster time course than BOLD signals [26] with the EEG oscillations actually eliciting the BOLD signal activations within several RSNs [27]. Synchronous EEG oscillations appear to bind together BOLD responses within RSNs in a frequency-dependent manner: long-distance integration of the BOLD response is coordinated by lower frequency (e.g., alpha, or 8–12 Hz) activity, while shorter-distance BOLD responses are coordinated by higher frequency (e.g., beta, or 12–20 Hz) activity [26], [28]–[29]. BOLD signal fluctuations within each RSN are accounted for by different combinations of rhythmic neuronal firing in the delta (0.5–4 Hz), theta (4–8 Hz), alpha, beta, and gamma (>20 Hz) frequency bands, and multiple frequencies are coupled to mediate brain operations [30]–[31]. Each functional network therefore has a distinct electrophysiological signature that is characterized by the synchronous oscillations of the neurons in that network [31]–[32]. In a combined fMRI/qEEG resting state study, Sadaghiani and colleagues showed that spontaneous fMRI fluctuations were strongly positively correlated with alpha band oscillations in a cingulo-insular-thalamic network, and
