The Correlation between the Sites of the Brain for Different Bandwidths of EEG in Interictal Paroxysmal rhythmic Activity: Using Wavelet-crosscorrelation Analysis

Abstract

Interictal paroxysmal rhythmic activity can appear in electroencephalography (EEG) in patients with mental disorders. The abnormal EEG were analyzed by wavelet-crosscorrelation analysis. The EEG were categorized as following: 2-4 seconds (A) and 0-2 seconds (B) before the appearance of the abnormal EEG; 2 seconds during the abnormal EEG (C); 0-2 seconds (D) and 2-4 seconds (E) after the abnormal EEG. Wavelet-crosscorrelation coefficients (WCC) in the theta and alpha bands for each segment were calculated in all patients. The results in the theta band showed that the abnormal connections between the sites in the brain could continue although the EEG seemingly recovered from the interictal paroxysmal rhythmic activity. The results in the alpha band showed that the normal connections between the sites in the brain could be weakened in the 2 seconds prior to the beginning of the interictal paroxysmal rhythmic activity in the EEG.

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“…The mean power spectra were normalized using the average power spectral values from the Control period to obtain relative power spectral density ratios in the theta 1 (4–6 Hz), theta 2 (6–8 Hz), alpha 1 (8–10 Hz), alpha 2 (10–12 Hz), alpha 3 (12–14 Hz), beta 1 (14–16 Hz), beta 2 (16–18 Hz), and beta 3 (18–20 Hz) bands . We adopted these eight frequency bands based on our previous research because EEGs contain several kinds of waves in various frequencies and these waves appear in different ways .…”

“…The mean power spectra were normalized using the average power spectral values from the Control period to obtain relative power spectral density ratios in the theta 1 (4-6 Hz), theta 2 (6-8 Hz), alpha 1 (8-10 Hz), [16]. We adopted these eight frequency bands based on our previous research [19,20] because EEGs contain several kinds of waves in various frequencies and these waves appear in different ways [21]. A TS consisting of 57 or 58 mean relative power spectral density ratios in eight frequency bands on 19 electrodes from EEG was obtained in 180 s ( Fig.…”