The EEG spectra of Alzheimer's disease.

Sixteen Alzheimer's and 16 non-Alzheimer's dementia patients, the two groups being matched for dementia, as well as 10 normal controls were given an EEG examination with 12 monopolar leads during an awake-resting condition. Power spectra (16 s) were obtained in 12 brain areas for 18 frequency bands (0-36 Hz). An 11-point dementia scale furnished the dementia scores. Analyses of variance were performed. Data confirmed earlier findings of an increase in slow activity and a decrease in fast activity for the demented groups. It further demonstrated that these EEG features were not related to dementia per se since the Alzheimer's group (matched for dementia) exhibited a spectral curve having a maximum at 1 Hz and an exponential asymptotic power characterized by decreasing power with increasing frequency without additional features or remnant of dominant activity. The study demonstrated that the decrease in frequency of alpha activity is perhaps more significant in identifying dementia of the non-Alzheimer type even though this characteristic may be present in the earlier stages of Alzheimer's dementia. It is hypothesized that the characteristics shown by the Alzheimer's group may be related to the presence of neurofibrillary tangles and plaques which are more prevalent in Alzheimer's patients.