EEG coherence in Alzheimer's disease

Area of Science:

• Neuroscience
• Clinical Neurology
• Biomedical Engineering

Background:

• Electroencephalography (EEG) coherence measures functional connectivity and synchronization of cortical activity.
• Alzheimer's disease (AD) is characterized by progressive cognitive decline and neuropathological changes affecting brain networks.

Purpose of the Study:

• To investigate EEG coherence alterations in patients with clinically probable Alzheimer's disease (AD).
• To quantify changes in cortico-cortical and cortico-subcortical connections in AD patients.

Main Methods:

• Recorded EEG from 10 AD patients (mild/moderate dementia) and 10 controls at rest, eyes-closed, using 16 electrodes.
• Calculated spectral parameters and coherence using a multichannel autoregressive model on 50 artifact-free, 1-second epochs.
• Analyzed alpha and delta frequency bands for coherence changes.

Main Results:

• Significant decrease in alpha band coherence observed in the AD group, especially in temporo-parieto-occipital areas.
• Alpha coherence reduction was more pronounced in patients with greater cognitive impairment.
• A few patients showed a significant increase in delta band coherence between frontal and posterior regions.

Conclusions:

• Reduced alpha coherence may indicate impaired cortico-cortical connections in AD.
• Increased delta coherence could reflect diminished subcortical cholinergic influence on cortical activity.
• EEG coherence analysis offers insights into the neurophysiological underpinnings of Alzheimer's disease.