EEG Coherence in Alzheimer's Disease

Kwak, Yong Tae; Hahm, Dong Seok; Han, Il Woo; Sam, Baik Jong

Abstract

BACKGROUND
EEG coherence can be used to evaluate the functional cortical connections and to get information about the synchronization of the regional cortical activity. We studied EEG coherence in patients affected by clinically probable Alzheimer's disease (AD) in order to quantify the modifications in the cortico-cortical or cortico-subcortical connections. METHODS: The EEGs were recorded in 62 AD patients and in 30 normal age-matched subjects from 16 electrodes with linked-ears reference. Spectral parameters and coherence were calculated by a multichannel autoregressive model using 20 artifact-free 2-sec epoch in normal controls and AD patients. RESULTS: In AD patients, alpha coherence in frontal field and theta, alpha interhemispheric coherence was significantly decreased, whereas alpha, beta coherence in posterior field was significantly increased. Some electrodes in the anterior field showed significant negative correlation with MMSE, whereas other electrodes in the posterior field showed significant positive correlation with MMSE. CONCLUSIONS: This study suggests that coherence is a useful tool for understanding electrophysiologic change of AD and for correlating with the severity of cognitive dysfunction. And these coherence changes can be interpreted as the effects of neuronal loss and neocortical disconnection.