Research On Forehead Soft Dry Electrode And Single-channel Eeg Preprocessing Technology

Electroencephalography(EEG)is a non-invasive method to record brain electrical activity and it has been widely used to study brain function due to its high temporal resolution.In recent years,mobile medical and wearable devices have developed rapidly.In order to meet the requirements of smaller size and computational complexity,these systems usually use a single-channel forehead EEG solution.The disadvantages of conventional wet electrodes,such as the need to apply conductive gels and their complicated operation,are not suitable for portable EEG systems.In addition,EEG signals often contain EMG artifacts.The existing artifact removal method requires multi-channel EEG signals,which limits the popularization and application of portable single-channel EEG systems.In order to solve the above-mentioned problems,we mainly did the following work:1.In order to solve the shortage of wet electrodes,we designed and manufactured a forehead flexible EEG dry electrode.The dry electrode is made of rubber substrate with conductive silver powder,and its contact surface with the scalp is designed as an arc-shaped curved surface.Compared with the planar electrode,this electrode has the advantages of closer contact with the scalp,larger skin contact area,and less slippage on the skin.In this paper,the electrode-skin contact impedance of the dry and wet electrodes was measured and compared at the forehead.At 10 Hz,the contact impedances of the two were 26.5 ± 16.2 k? and 12.8 ± 5.7 k?,respectively.The average correlation coefficient between the dry and wet electrodes in the EEG acquisition and comparison experiment was 0.95.In the alpha rhythm test experiment the results between the dry and wet electrodes is similar,showing obvious characteristics.In summary,the dry electrode designed in this paper has similar performance as the wet electrode and can be widely used in daily EEG acquisition.2.In order to remove EMG artifacts in single-channel EEG signals,we proposed a method of artifact removal based on SSA-MCCA.This method does not require multi-channel EEG signals and has low computational complexity.It is very suitable for portable single-channel EEG systems.In this paper,SSA-MCCA was compared with SSA-ICA and EEMD-CCA quantitatively by using three kinds of simulated EEG data with different input SNR.When the input signal-to-noise ratio was-5dB,the correlation coefficients of the three methods were 0.93 ± 0.03,0.90 ± 0.02,and 0.85 ± 0.01,and the signal-to-noise ratio improvement were 13.86 ± 1.53,12.22 ± 0.91,and 10.48 ± 0.36,respectively.We also used the actual EEG data to further verify the practicability of this method.The results showed that this method can well remove the EMG artifacts in single-channel EEG signals.3.We designed and implemented a simple and feasible portable forehead EEG acquisition and processing system based on the designed forehead flexible dry electrode and SSA-MCCA method combined with Neuro Sky's TGAM module.We used the system to collect and process EEG in real scenes.The experimental results showed that the system can reliably collect the EEG signals of the subjects on the basis of the portable,and can effectively remove the EMG artifacts in the EEG signals,which verified the effectiveness of the system.