EEG Coherence in Controls, Mild Cognitive Impairment and Different Stage of Alzheimer's Disease

Kwak, Yong Tae

Abstract

BACKGROUND: EEG coherence can be used to evaluate the functional electrical connections between different cortical regions. We compare EEG coherences among younger controls (YC), elderly controls (EC), mild cognitive impairment (MCI), and different stages of Alzheimer's disease (AD) in order to clarify the electrophysiological changes of aging and process of dementia.
METHODS
The EEGs were recorded in 29 YC, 37 EC, 22 MCI, 11 CDR 0.5, 42 CDR1, 51 CDR2, 53 CDR3 AD patients from 19 electrodes with linked-ears reference. Anterior and posterior intrahemispheric, far interhemispheric, and interhemispheric coherence were calculated in study subjects.
RESULTS
Elderly controls showed increased anterior local coherence and decreased posterior local coherence compared to the other groups. This results in diminished posterior-anterior differences compared to that of young controls. Compared to elderly controls, significantly higher far coherence values was noted in the theta, alpha, beta band of MCI, theta, beta band of CDR0.5, beta band of CDR1, CDR2, CDR3. In MCI, the delta band of anterior local coherence was significantly decreased compared to mild to moderate AD, and theta, alpha band of posterior local coherence was significantly increased compared to CDR3 of AD.
CONCLUSIONS
The coherence changes of controls, MCI and AD is not simple and not specific enough to differentiate the MCI and early AD from the other groups. These complex patterns may reflect the pathophysiological findings of cholinergic change of AD, and we need to increase the understanding of the electrophysiological relationships among aging, MCI and various stages of AD.