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Antero-posterior EEG changes during the wakefulness-sleep transition
L De Gennaro1, M Ferrara, G Curcio
1Dipartimento di Psicologia, Sezione di Neuoroscienze, Università degli Studi di Roma La Sapienza, Via dei Marsi, 78, 00185, Rome, Italy. luigi.degennaro@uniroma1.it
Summary
The human sleep electroencephalogram (EEG) shows distinct brain topography changes during the wakefulness-sleep transition. Alpha rhythm shifts anteriorly, with early synchronization in frontal areas, suggesting a revision of EEG band functions during sleep onset.
Area of Science:
- Neuroscience
- Sleep Medicine
- Brain Imaging
Background:
- Understanding the electroencephalogram (EEG) topography during sleep onset is crucial for deciphering brain activity shifts.
- Previous research has not fully elucidated the antero-posterior distribution of EEG frequencies during the transition from wakefulness to sleep.
Purpose of the Study:
- To investigate the brain topography of human sleep EEG along the antero-posterior axis during the wakefulness-sleep transition.
- To analyze EEG changes using both single Hz and grouped-frequency analyses.
Main Methods:
- Calculated EEG power values across a 1-28 Hz frequency range with 1 Hz resolution in 7 normal subjects.
- Assessed topographical changes using scalp recordings (e.g., Fpz-A1, Cz-A1, Oz-A1) aligned to sleep onset (SO) stage 2.
- Employed both single Hz and grouped-frequency analyses for comprehensive evaluation.
Main Results:
- Before sleep onset (SO), slow frequencies (<7 Hz) were prominent anteriorly, while faster frequencies (>8 Hz) predominated posteriorly.
- After SO, slow frequencies increased in centro-frontal areas, and sigma frequency activity peaked in centro-parietal regions.
- Alpha rhythm showed anterior spreading, and grouped-frequency analysis confirmed distinct topographical changes related to SO.
Conclusions:
- The alpha rhythm actively spreads anteriorly during the wakefulness-sleep transition.
- Anterior brain areas exhibit early synchronization of EEG activity.
- The functional interpretation of EEG bands, particularly alpha rhythm, may require revision concerning sleep onset.