Submitted to Electroencephalography and Clinical Neurophysiology

Objective: Breaking the skin when applying scalp electroencephalographic (EEG) electrodes creates the risk of infection from blood-born pathogens such as HIV, Hepatitis-C, and Crutzfeld-Jacob Disease. Modern engineering principles suggest that excellent EEG signals can be collected with high scalp impedance ( 40 k) without scalp abrasion. The present study was designed to evaluate the effect of electrode-scalp impedance on EEG data quality. Methods: The first section of the paper reviews electrophysiological recording with modern high input-impedance differential amplifiers and subject isolation, and explains how scalp-electrode impedance influences EEG signal amplitude and power line noise. The second section of the paper presents an empirical test of EEG data quality as a function of scalp-electrode impedance for the standard frequency bands in EEG and ERP (event-related potential) recording. Results: There was no significant change in amplitude of any EEG frequency as scalp-electrode impedance increased from less than 5 k (abraded skin) to 40 k (intact skin). As expected, 60 Hz noise increased linearly as a function of the absolute impedance and impedance mismatch between the measurement and reference electrodes. Conclusion: With modern high input-impedance amplifiers and accurate digital filters for power line noise, high-quality EEG can be recorded without skin lesions.