Quantitative characteristics of EEG in Alzheimer’s disease during cognitive tasks

Abstract

In Alzheimers disease (AD) the EEG changes are rather diffuseand most expressed in moderate and severe cognitive disorders.Pathological changes of spectral power and EEG coherence areassumed to be related with the degree of cognitive deficit. Theaim of this study: comparative analysis of spectral power andEEG coherence and their reactivity during functional tasks inAD patients with mild and moderate dementia and in agematchedhealthy control subjects. Twenty two AD patients withmild-to-moderate dementia and 25 controls were examined. Allpatients underwent EEG recordings with analysis of spectralpower of the main rhythms, as well as with analysis of intra- andinter-hemispheric coherence and their dynamics during functionaltasks. We found an increase in slow-wave activity (deltaand theta rhythms) and a decrease in alpha activity in frontal,parietal and temporal regions of the brain. Intra- and interhemisphericcoherence was significantly lower in frontal, parietaland temporal regions in AD patients compared to controls.EEG pattern was more obvious after functional tests. One mayconclude that changes of spectral power and EEG coherenceseem to be a sensitive indicator of cognitive decline at very earlystages of neurodegenerative process.

Keywords

• alzheimer’s disease
• eeg
• markers of cognitive decline