Coherence Validation of Alternative Sleep EEG Electrode Placements Using Wavelet Transform

10.5405/jmbe.1511

Shih-Chung Chen；Aaron Raymond See；Chun-Ju Hou；Yeou-Jiunn Chen；Chih-Kuo Liang；Po-Yang Hou；Wen-Kuei Lin

Sleep encephalography (EEG) ； Prefrontal EEG ； Discrete wavelet transform ； Correlation coefficient ； Jackknife analysis ； Magnitude-squared coherence

Journal of Medical and Biological Engineering

34卷6期（2014 / 12 / 01）

528 - 534

英文

Recent studies on automated sleep stage classification have started to adopt alternative sleep encephalography (EEG) electrode placements on the forehead as opposed to the traditional C3-C4 placement. The current study determines the validity of adopting the prefrontal EEG electrode placement. First, EEG signals were decomposed into four harmonic bands using the discrete wavelet transform and their power spectrum densities were extracted for comparison. The correlation coefficients of both signals were calculated and jackknifed to determine an unbiased statistical value. The signal and its power spectrum displayed moderate to very strong values of the correlation coefficient, respectively, with minute standard errors and biases. A strong coherence is exhibited between both electrode placements as viewed from the power spectra of different sleep stages. The magnitude-squared coherence values indicate that the reduction in the coefficient values for the beta band was due to a low correlation in a certain frequency band. Manual sleep stage classification was also conducted by a sleep technician and sleep stage classification software, with consistent results obtained. Sleep stage scoring using both methods indicated substantial agreement for the standard and alternative electrode placements. In conclusion, this work shows a strong coherence for the prefrontal and standard electrode placements and corroborates the hypothesis of using the alternative placements for performing quick, convenient, and efficient measurement and analysis of EEG signals.