Researchers at the University of Trieste have found that using a nonlinear approach in EEG analysis in combination with a cognitive task during EEG recordings could make the difference in highlighting EEG alterations at very early stages of cognitive impairment. This EEG protocol may therefore be a practical and non-invasive tool in the clinical context to identify subjects for second level diagnostic examinations for Alzheimer's Disease (AD).
Mild (MCI) and Subjective Cognitive Impairment (SCI) are conditions at risk of developing Alzheimer's disease. Differential between normal aging at early stages can be really challenging; available biomarkers need to be combined and can be quite invasive and expensive.
The researchers recruited 11 MCI, 8 SCI and 7 healthy subjects as controls (CS), all matched for age and education; they performed neuropsychological assessment and EEG recording, at resting state and during a mental memory task, and they used both classical spectral measures and nonlinear parameters to characterize EEGs.
During cognitive tasks, α-band power reduction was found predominantly in frontal regions in SCI and CS, diffused to all regions in MCI; moreover, decreased EEG complexity was found in SCI compared to controls. The α-band power attenuation restricted to frontal regions in SCI during a free recall task (involving frontal areas), suggests that MCI patients compensate for encoding deficit by activating different brain networks to perform the same task. Furthermore, EEG complexity reduction - that has been found already in SCI - could be a possible early hallmark of AD. The researchers suggest that this analysis may be applied in clinical routine as a diagnostic and prognostic tool in subjects with complaining of initial cognitive impairment.
The study, 'Memorization test and resting state EEG components in mild and subjective cognitive impairment', co-authored by Giulia Mazzon and his collaborators, all of the University Trieste, was published recently in Current Alzheimer Research.
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Reference: Mazzon G et al, (2018). Memorization Test and Resting State EEG Components in Mild and Subjective Cognitive Impairment. Current Alzheimer Research, Vol 15, Issue 9. DOI: 10.2174/1567205015666180427114520