Fig. 7 illustrates a typical experimental setting for simultaneous fMRI-EEG recordings. Carbon electrodes and current-limiting resistors are often used to minimize the MR susceptibility effect and the safety concerns [155]. Short copper wires connecting electrodes should be twisted, bundled and stabilized using taps and sandbags. Local amplifiers are preferred for signal amplification and digitization. Optical fibers are used for transmitting signals to the recording devices outside the MR environment. An ECG lead is placed at the subject's back to record a temporal marker for every heart beat. The onsets of fMRI volume acquisitions are recorded by connecting the TTL output from the scanner to the EEG recording device. Both the ECG and the scanner TTL signals are useful for the artifact removal during the post-processing. It may also be desirable to synchronize the EEG sampling with the clock driving the fMRI pulse sequence to avoid any phase-asynchrony of the GA.
