Disturbed fluctuations of resting state EEG synchronization in Alzheimer's disease

C J Stam, T Montez, B F Jones, S A R B Rombouts, Y van der Made, Y A L Pijnenburg, Ph Scheltens

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OBJECTIVE: We examined the hypothesis that cognitive dysfunction in Alzheimer's disease is associated with abnormal spontaneous fluctuations of EEG synchronization levels during an eyes-closed resting state.

METHODS: EEGs were recorded during an eyes-closed resting state in Alzheimer patients (N=24; 9 males; mean age 76.3 years; SD 7.8; range 59-86) and non-demented subjects with subjective memory complaints (N=19; 9 males; mean age 76.1 years; SD 6.7; range: 67-89). The mean level of synchronization was determined in different frequency bands with the synchronization likelihood and fluctuations of the synchronization level were analysed with detrended fluctuation analysis (DFA).

RESULTS: The mean level of EEG synchronization was lower in Alzheimer patients in the upper alpha (10-13Hz) and beta (13-30Hz) band. Spontaneous fluctuations of synchronization were diminished in Alzheimer patients in the lower alpha (8-10Hz) and beta bands. In patients as well as controls the synchronization fluctuations showed a scale-free pattern.

CONCLUSIONS: Alzheimer's disease is characterized both by a lower mean level of functional connectivity as well as by diminished fluctuations in the level of synchronization. The dynamics of these fluctuations in patients and controls was scale-free which might point to self-organized criticality of neural networks in the brain.

SIGNIFICANCE: Impaired functional connectivity can manifest itself not only in decreased levels of synchronization but also in disturbed fluctuations of synchronization levels.

Original languageEnglish
Pages (from-to)708-715
Number of pages8
JournalClinical neurophysiology
Issue number3
Publication statusPublished - Mar 2005


  • Aged
  • Aged, 80 and over
  • Alzheimer Disease/physiopathology
  • Brain Mapping
  • Cerebral Cortex/physiopathology
  • Cortical Synchronization
  • Female
  • Humans
  • Male
  • Middle Aged
  • Neuropsychological Tests
  • Rest/physiology
  • Time Factors

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