The actual recording of scalp potentials—picking up the minute voltages—may be one of the lesser worries for homogeneity across participating cohorts, given today's high‐quality research EEG equipment. Large individual differences in oscillatory amplitudes and other biomarkers exist in EEG signals that will not be affected crucially by amplifier quality, especially when enough data are available per subject for stable estimates. Likewise, active versus passive electrodes—the use of which is generally linked to the choice of apparatus—is not expected to show large effects on EEG parameters as long as dry electrodes are avoided (Laszlo et al., 2014; Mathewson et al., 2017).
