Spectral Analysis of EEG Patterns in Normal Adults

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1 Spectral Analysis of EEG Patterns in Normal Adults Kyoung Gyu Choi, M.D., Ph.D. Department of Neurology, Ewha Medical Research Center, Ewha Womans University Medical College, Background: Recently, the quantitative analysis of biological signals has been possible due to the development of digital machines, new mathematical theories including the nonlinear time series, chaotic and dynamic theories, and convenient statistical tools. The characteristics of biological signals however, can not analyzed solely through visual interpretation or judgement. The author statistically analyzed the EEG data of normal adults by using spectral analysis. Methods: Quantitative EEG analysis was performed in 5 normal adults in order to analyze differences between the left and right hemispheres and interelectrode differences of the power spectrum of variable frequency bands. The results were statistically analyzed using SPSS. Results: The spectral powers of the left frontal delta, the right parietal theta and left frontal alpha were significantly higher than the opposite sides. In the analysis of interelectrode difference, the temporal beta band power was significantly higher than the frontal areas. There were no significant interelectrode differences in other frequency bands. C o n c l u s i o n s: The results of this study show that there are differences between the visually perceived EEG patterns and the frequency domain analysis. These findings suggest that EEG waves on recording papers are the results of interference among variable frequency bands. The continued analysis of EEG by using nonlinear parameters will be beneficial as a powerful tool in understanding the neural network dynamic in the brain. J Kor Neurol Ass 17(3):384 ~ 388, 1999 Key Words : Spectral analysis, Power spectrum, Electroencephalograph Kyoung Gyu Choi, M.D. 384 Copyright 1999 by the Korean Neurological Association

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3 Table 1. Mean power spectrum value of each electrode. Low Delta Theta Alpha Beta Gamma High Total Fp1-F F3-C C3-P P3-O FP2-F F4-C C4-P P4-O FP1-F F7-T T3-T T5-O FP2-F F8-T T4-T T6-O Fz-Cz Cz-Pz T1-A T2-A Low : < 0. 5, Delta:0.5-4, Theta:4-8, Alpha:8-12, Beta:12-20 Gamma : 20-40, High: >40 Table 2. The result of paired t-test of power spectra between left and right side. Wave bands delta theta low alpha * : p<0.05 Electrodes (P-value) Fp1-F3 Fp2-F4(0.040)* C4-P4 C3-P3(0.033)* Fp2-F8 Fp1-F7(0.044)* F7-T3 F8-T4(0.040)* Table 3. The result of oneway-anova between each electrode. Wave bands beta * : p<0.05, **: p<0.01 Electrodes (P-value) Fp1-F3 T3-T5(0.022)* FP2-F4 F7-T3(0.028)* Fp2-F4 T3-T5(0.003)** FP2-F4 T6-O2(0.022)* FP2-F8 T3-T5(0.003)** FP2-F8 F7-T3(0.025)* FP2-F8 T6-O2(0.019)* FP2-F8 T5-O1(0.032)* Figure 1. Examples of the diagram of spectral analysis on electrode F2-F4 (a) and T3-T4 (b). 386 J Kor Neurol Ass / Volume 17 / May, 1999

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