Abstract
We investigated the correlation and time-lag (LAG) between the sites of the brain for different durations of epileptiform discharges, using wavelet-crosscorrelation (WCC) analysis. Electroencephalography (EEG) was classified into two epochs according to the epileptiform discharge durations, as follows: short run, 2-3 seconds; and long run, 3 seconds or more. Both runs were categorized into before, during, and after the epileptiform discharges. WCC coefficients and LAG in the 6 and 8 Hz bands for each segment were calculated in all the patients. The results of the comparison among all the electrodes in both runs showed that the correlation during the epileptiform discharges was higher than before and after the epileptiform discharges. In the 6 Hz band, in the short run, the results of the comparison among the temporal region electrodes showed that the correlation and LAG between the sites could be stronger in the 2 seconds immediately prior to the beginning of the epileptiform discharges in the EEG. In the long run, the results of the comparison among the temporal region electrodes showed that high correlation and LAG between the sites could be stronger in the 2-4 seconds immediately prior to the beginning of the epileptiform discharges and 2-4 seconds after to the epileptiform discharges in the ipsilateral hemisphere and contralateral hemisphere. It can be suggested that the difference in the duration of the epileptiform discharges may be caused by the balance between the suppressive and excitatory processes in the brain, before and after epileptiform discharges.
