Coherence of the electroencephalogram during the first sleep cycle

Clin Neurophysiol. 2005 May;116(5):1088-95. doi: 10.1016/j.clinph.2004.12.002. Epub 2005 Jan 24.


Objective: The increasing amplitude of the electroencephalogram (EEG) during non-rapid eye movement sleep implies a progressive synchronization of neuronal activity. We sought to characterize the spatial relationship of cortical activity at different frequencies during the first sleep cycle, focusing on sleep stages 3 and 4 (slow wave sleep).

Methods: Sleep EEGs were obtained at home from six adults using a portable recorder. Signal power and magnitude squared coherence were measured during the first sleep cycle. Spectra obtained from bipolar and common reference derivations were compared.

Results: During slow wave sleep, signal power is highest in the delta frequency band and regional coherence below 5 Hz is broadly distributed. Although signal power in the alpha and sigma frequency bands is lower, peaks of regional coherence in those bands are similar to or higher than delta-band coherence. Regional coherence during slow wave sleep is differentially distributed with a 14 Hz component in central and posterior regions and a 10 Hz component in frontal and central regions.

Conclusions: Ten and 14 Hz rhythms are an essential component of slow wave sleep.

Significance: The interpretation of scalp EEG power and coherence spectra is limited by the lack of a satisfactory recording reference. However, conclusions can be made by comparing and contrasting results from both bipolar and common reference recordings.

MeSH terms

  • Adult
  • Brain / physiology*
  • Brain Mapping*
  • Electroencephalography*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Sleep Stages / physiology*