INTERHEMISPHERIC AND INTRAHEMISPHERIC EEG CORRELATION DURING SLEEP AND WAKEFULNESS

Inter- (INTERr) and intrahemispheric (INTRAr) electroencephalographic (EEG) correlations were assessed in eight young male adults during wak efulness with eyes closed before going to sleep, and during stage 2, s tage 4 and paradoxical sleep (PS) on the second night spent at the lab oratory. Pearson product-moment correlations were calculated between E EG signals of every pair of electrodes (C3, C4, F3, F4, T3, T4) for si x bands and for every 0.5 Hz from 1.5 to 15 Hz. Previous results of hi gher INTERr during sleep compared to during wakefulness were confirmed for the delta and theta bands during stage 2 sleep and PS and for sle ep spindles during stage 2 sleep. The present results extend these fin dings to INTERr between F3 and F4 and during stage 4 sleep. INTRAr of 1.5-6.5 and 11-15 Hz was significantly higher during stages 2 and 4, w hereas during PS INTRAr did not change. These data show that cortical changes during sleep are also observed in functional differentiation b etween cortical sites. Inter- and intrahemispheric differentiation is attenuated during stage 2 and 4 sleep, whereas during PS only interhem ispheric differentiation is attenuated but intrahemispheric differenti ation maintains similar levels of wakefulness. The attenuation of cort ical differentiation may be of relevance for the understanding of ment al activity changes during sleep.