EEG upper/low alpha frequency power ratio and the impulsive disorders network in subjects with mild cognitive impairment.

The ventral striatum-nucleus accumbens network has been associated with impulsive behavior in subjects with early cognitive impairment; in Alzheimer's disease (AD) modifications of basal ganglia have been also demonstrated. Moreover, the increase of EEG alpha3/alpha2 frequency power ratio has been investigated as EEG marker in subjects with mild cognitive impairment (MCI) who will develop AD. In the present study we have detected the relationship between upper alpha/low alpha ferquency power ratio and specific gray matter (GM) changes in the basal ganglia in subjects with MCI. Electroencefalographic (EEG) recording and high resolution 3D magnetic resonance imaging (MRI) were taken in 74 MCI subjects. In each subject the alpha3/alpha2 EEG frequency power ratio was estimated as EEG biomarker. Three groups were obtained according to increasing tertiles values of the biomarker. Through the Voxel Based Morphometry (VBM) technique, GM density differences between groups were evaluated. Results show that subjects with lower a3/a2 and middle a3/a2 ratio ratio showed greater gray matter reduction in the Nucleus Accumbens and the head of Caudate Nucleus as compared to subjects with higher a3/a2 ratio. Our study indicates that the a3/a2 frequency power ratio was associated with increase of grey matter density inside the impulsivity network of MCI patients more likely develop AD.