Motion artifact reduction in EEG recordings using multi-channel contact impedance measurements

Dry-contact electrodes have paved the way for easy-to-use electroencephalography (EEG) systems with minimal setup time, which are of particular interest in ambulatory as well as real-life environments. However, the presence of motion artifacts forms a major obstacle for such systems. In previous studies, it has been shown that continuous electrode-tissue impedance monitoring can be used to handle motion artifacts. In this paper, we demonstrate that the in-phase and quadrature components of the contact impedance provide complementary information that can be used to improve the prediction of motion artifacts. Furthermore, we demonstrate that the prediction of motion artifacts at one electrode can be further improved by also incorporating the impedance measurements at other electrodes. With this, we propose a motion artifact reduction algorithm based on a multi-channel linear prediction (MLP) filter. Although the MLP filter is not able to completely remove motion artifacts, a substantial reduction can indeed be achieved. © 2013 IEEE.status: publishe

Comb-shaped Polymer-based Dry Electrodes for EEG/ECG Measurements with High User Comfort

Soft, comfortable polymer-based dry electrodes are fabricated. Impedance and biopotential measurements are carried out to compare the performance of conventional gel electrodes with our dry electrodes. The impedance of our dry electrodes is reduced by adding more conductive additives to the polymer material. To further lower the impedance, two skin pretreatment techniques are evaluated regarding their influence on skin impedance. However, these techniques are found to have only temporary beneficial effects. Finally biopotential measurements (both ECG and EEG) are performed using our soft polymer electrodes. The ECG signal acquired with both gel and our polymer electrodes demonstrates high degree of similarity. Therefore, heart beat detection is straightforward. To enable monitoring of EEG signals with smaller amplitudes, our dry electrodes need to be combined with pre-amplifiers. Initial EEG tests show that the alpha waves are clearly identifiable with the dry electrodes when subjects close their eyes. Based on the results, combining with sophisticated signal acquisition electronics, the dry electrodes provide a high user comfort solution for high quality biopotential measurements, even on very hairy skin