Do tripolar concentric ring electrodes record sensorimotor rhythms better?

Author: Khoa Tien Tang

Tang, Khoa Tien, 2021 Do tripolar concentric ring electrodes record sensorimotor rhythms better?, Flinders University, College of Science and Engineering

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Sensorimotor rhythms (SMRs) were recorded over the sensorimotor cortex in the preparation, and during imagine or performing of an observed action. According to previous studies, it is used to implement classification in the Brain-Computer Interface with its spatial and spectral features. However, the majority of these studies were conducted using traditional electrodes. A new cutting-edge called the tripolar concentric ring electrode (tCRE) was developed based on approximating the surface Laplacian came from the idea of the nine-point difference method. It was expected to increase the spatial resolution as well as effectively reduce movement artefacts such as eye or limbs movement. Therefore, the ultimate goal of this project was to provide more evidence of the advantages and disadvantages of recording SMRs using tCRE. Three smaller goals have been done including designing and executing a proper experiment pilot, success in recording SMRs in different conditions, and finally plotting and exploring the event-related (de)synchronisation (ERD/ERS) relative to participant response. There are six participants’ EEG data was recorded in four different conditions: hand tapping, imagine hand tapping, foot-tapping, and imagine foot tapping. 40 channels were recorded including 20 tCRE electrode channels and 20 traditional electrode channels. Raw data was cleaned by provided function from EEGLAB, reconstructed with principal component analysis to evaluate valuable data. Then, its spectrogram was calculated by using the continuous wavelet transform (CWT) with the frequency range 8-12 Hz to only remain SMRs. The ERD/ERS was calculated by normalising to the baseline for observing the decrease or increase trends. Unfortunately, the results from this project were not enough to conclude the main goal as both types of electrode shows the same performance in terms of ERD/ERS. Even though tCRE electrode showed an advantage in reducing noises, some of its channels were considered as bad channels and it show a worse performance when observing ERD. Overall, the approach of this project was proved as contributing an idea for assessment and there are spaces for further studies

Keywords: Sensorimotor Rhythms, tCRE, traditional electrodes, ERD/ERS.

Subject: Engineering thesis

Thesis type: Masters
Completed: 2021
School: College of Science and Engineering
Supervisor: Kenneth Pope