Global approach to multichannel electroencephalogram analysis for diagnosis and clinical evaluation in mild Alzheimer's disease.

To establish an early diagnosis of Alzheimer's disease (AD), we evaluated brain spatial dynamics and cognitive function in mild AD. Seventeen patients with the diagnosis of mild AD and 17 age-matched controls were examined for Omega (global complexity), Sigma (total power) and Phi (generalized frequency) by 19-channel electroencephalography (EEG). As a result, the mild AD group showed significantly higher Omega values than the control group. The Phi values were highly correlated with the Mini-Mental State Examination scores and the full IQ and performance IQ scores of the Japanese Wechsler Adult Intelligence Scale Revised. These results indicate an increase in spatial complexity of the brain electric field in mild AD, as well as a close relationship between slowing of the global frequency of field changes and the cognitive decline in mild AD.