Investigating the impact of force and movements on impedance magnitude and EEG

The success of applying dry sensor technology in measuring electroencephalogram (EEG) signals will have a significant impact on a wider adoption of brain activity monitoring in ambulatory as well as real life solutions. The presence of motion artifacts is the major obstacle in applying dry sensors for long-term EEG monitoring. In this paper we assess the impact of external forces applied on a dry EEG electrode as well as the impact of head and body movements on the electrode-tissue contact impedance and the EEG signal. The data collection method and the preliminary correlation analysis are presented. The analysis demonstrates that the impedance magnitude and EEG changes are highly correlated when artifacts are induced by the application of force or head and body movements, only in case these artifacts are short (less than 3s) and exhibit regular pattern. The correlation between the EEG and impedance magnitude is lower for longer artifact segments, especially the ones containing artifacts with irregular movements or large variations in the applied force. This indicates a time-dependent, non-linear relation between the artifact-related phenomena, impedance magnitude, and EEG.