As the above techniques appear promising, simultaneous fMRI-EEG recordings have proven to provide reasonable data quality for event-related potentials, frequency-specific oscillatory activities and rhythmic modulations. To attest this point, three control experiments have been conducted with the data shown in Fig. 8. In an experiment using 2-Hz full-screen visual stimuli [174], similar visual evoked potentials (VEP) were obtained from the EEG data recorded with or without concurrent fMRI scans (Fig. 8.A). No obvious distortions were found in either MRI or fMRI [174]. In another experiment with 9-Hz visual stimuli, sustained oscillatory EEG signals at the stimulus frequency, known as the steady-state visual evoked pontetials (SSVEP), were found at occipital electrodes (Fig. 8.B) [127]. The last example involved a self-paced eye-open-and-close task, which is known to change the occipital rhythmic EEG in the alpha band (8~12Hz). Such an expected rhythmic modulation was clearly observed from the time-frequency representation of the EEG data at the occipital electrodes (Fig. 8.C) [127].
