Alpha and Theta EEG Rhythms Activity Reveal Deep Changes in Resting Brain State in Subjects with Prodromal Alzheimer's Disease

The increase of EEG alpha3/alpha2 frequency power ratio has been associated with AD-converters subjects with mild cognitive impairment (MCI) as well as a reduction in the regional cerebral blood flow (rCBF). In this study, the association between alpha3/alpha2 frequency power ratio with rCBF changes in subjects with MCI was evaluated. The alpha3/alpha2 frequency power ratio was computed in 27 subjects with MCI. Two groups were obtained according to the median values of alpha3/alpha2, at a cut-off of 1.17. In the groups so obtained, the correlation between brain perfusion and EEG markers were detected. In the MCI group with the alpha3/alpha2 frequency power ratio above 1,17 as compared to the group with alpha3/alpha2 frequency power ratio below 1.17 there was: 1) a constant trend to lower rCBF values; 2) smaller hippocampal volumes; 3) higher theta frequency power. The higher EEG alpha3 /alpha2 frequency power ratio individuates two different group of MCI subjects. A complex interplay between alpha and theta rhythms activity MCI patients is suggested in patients with prodromal Alzheimer's disease.