Background: Mild (MCI) and Subjective Cognitive Impairment (SCI) are conditions at risk
of developing Alzheimer’s disease (AD). Differential between normal aging at early stages can be really
challenging; available biomarkers need to be combined and can be quite invasive and expensive.
Objective: The aim of this pilot study is to examine possible EEG alterations in MCI and SCI compared
to controls, analyzing if a cognitive task could highlight early AD hallmarks.
Method: We recruited 11 MCI, 8 SCI and 7 healthy subjects as controls (CS), all matched for age and
education. Neuropsychological assessment and EEG recording, at resting state and during a mental
memory task, were performed. Classical spectral measures and nonlinear parameters were used to characterize
Results: During cognitive task, 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.
Conclusion: This study draws attention on the importance of nonlinear approach in EEG analysis and
the potential role of cognitive task in highlighting EEG alterations at very early stages of cognitive impairment;
EEG could therefore have a practical impact on dementia diagnosis.