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Background : Sleep EEG is not an inactive electrical phenomenon but a active restorative process which is not understood in detail. Understanding stage2 sleep EEG with K complex and sleep spindle can be helpful for the demonstration of sleep physiology related with EEG source generation by specific brain regions. This study has been performed for better understanding stage2 sleep from electrical point of view using ICA (Independent Component Analysis) method. Methods : Stage2 sleep EEG was recorded from 23 normal subjects. Independent EEG components were investigated after running ICA with individual EEG followed by group IC analysis including scalp topography, IC dipole source localization, and percent variance analyses. Results : After applying inclusion criteria to identified IC's from each subjects, three major components were obtained. They are anterior cingulate (IC_AC), midline frontal (IC_MF), and midline parietal (IC_MP) components. They explained 43.4% of the whole stage2 sleep EEG (20.3% by IC_MF, 14.5% by IC_AC, and 8.6% by IC_MP). Conclusions : Significant part of stage2 sleep EEG was generated by midline structures such as anterior cingulate, midline frontal and midling parietal regions which are related with thalamocortical mechanism for the generation of sleep phenomenon. Further analysis can clarify the electrophysiological basis of sleep EEG.

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