Abstract
The aim of the study was to elaborate the specific quantitative EEG indicators, which can objectify a degree of cognitive impairment and make an assessment of the dementia depth more precise. In our study we investigated 35 unmedicated patients with the diagnosis of probable Alzheimer's disease, with various stages (mild, moderate, severe) of dementia.
The 60-seconds artefact-free EEG epochs were evaluated by means of computer analysis resulting in EEG spectrum and coherence values (delta, theta, alpha 1, alpha 2, beta 1 and beta 2). Among various EEG indicators, a decrease of long intrahemispheric alpha coherence and increase of the same delta coherence was found to be most significantly correlated to the degree of dementia.
Combining six variables from the spectrum and coherence analysis by means of the multiple regression model we could predict the dementia depth (represented by calculated value of Mini Mental State Test). The results suggest that the EEG can supplement the clinical examination by providing an independent assessment of the depth of dementia.
The results also suggest that the EEG coherences are of particular interest in dementia, being an indicator of the impaired signal transfer between various parts of the brain cortex.