Quantitative Electroencephalography and Low Resolution Electromagnetic Tomography Imaging of Alzheimer’s Disease

Objective-The EEG abnormalities of Alzheimer’s disease (AD) patients are characterized by increased slow wave activities and reduced asymmetry between the two hemispheres. We attempted to find the specific spatio-temporal EEG pattern of AD through quantitative EEG (qEEG) and the source localization of specific frequency bands. Methods-The AD group consisted of 22 patients who fulfilled the DSM-IV criteria of AD with no space occupying lesions confirmed by brain CT or MRI. The normal control (NC) group consisted of 27 subjects with no personal history of psychiatric or neurological abnormalities. We performed qEEG, compared the hemispheric asymmetry between the AD and NC groups, and tried to obtain source imaging of each frequency band using low resolution electromagnetic tomography (LORETA). Results-Compared with the NC group, the AD patients had significantly increased slow wave activities of the theta (4-7 Hz) and delta waves (1-3 Hz) over all of the electrodes. There was no statistically significant asymmetric difference between the AD and NC groups. The slow waves of the AD patients were dominant in the right hemisphere compared to the NC subjects. Increased theta wave activity was observed, especially in Brodmann area 40 (inferior parietal lobule) in the AD patients compared with the NC subjects. Increased delta wave activity was observed especially in Brodmann area 7 (postcentral gyrus) in the AD patients compared with the NC subjects. The MMSE score had a significant negative correlation with the theta waves and a positive correlation with the alpha waves in the AD patients. There was a positive correlation between the duration of illness and the theta waves in the AD patients. Conclusions-Our results showed that AD patients had increased theta and delta wave activity in the right parietal areas, which reflect their decreased brain function in these regions. Our results suggest that qEEG and LORETA imaging are useful tools for detecting and evaluating AD.