Temporo-Parietal Brain Network Impairment Is Related To EEG ALPHA3/ALPHA2 Power Ration in Prodormal Alzheimer’s Disease

Abstract

Background: Reliable biomarkers are the new frontier for an early diagnosis of Alzheimer's disease and to monitor therapeutic options Objective: Volume reduction in temporo-parietal network is associated to mild cognitive impairment (MCI) due to Alzheimer disease (AD). The increase of EEG alpha3/alpha2 ratio has been associated with AD-converter MCI subjects. We investigated the association of alpha3/alpha2 ratio with patterns of cortical thickness in MCI. Methods: 74 adult subjects with MCI underwent clinical and neuropsychological evaluation, electroencephalogram (EEG) recording and high resolution 3D magnetic resonance imaging (MRI). Alpha3/alpha2 power ratio as well as cortical thickness was computed for each subject. Three MCI groups were detected according to increasing tertile values of alpha3/alpha2 and difference of cortical thikness among the groups estimated. Pearson’s r was used to assess the topography of the correlation between cortical thinning and memory impairment. Results: High a3/2 group had total cortical grey matter (CGM) volume reduction of 471 mm2 than Low a3/ a2 group (p<.001). High a3/2 group showed a similar but less marked pattern (160 mm2) of cortical thinning when compared to Middle a3/a2 group (p<.001). Moreover, high a3/2 group had wider cortical thinning than other groups, mapped to the Supramarginal and Precuneus bilaterally. No significant cortical thickness difference was found between Middle and Low a3/a2 groups. Conclusion: High EEG alpha3/alpha2 ratio was associated with impairment of temporo-parietal cortical brain in MCI subjects. The combination of EEG alpha3/alpha2 power ratio and cortical thickness measure could be useful for identifying individuals at risk for progression to AD dementia and may be of value in clinical context.