Abstract
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 language | English |
|---|---|
| Pages (from-to) | 708-715 |
| Number of pages | 8 |
| Journal | Clinical neurophysiology |
| Volume | 116 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - Mar 2005 |
Keywords
- 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