Topography of EEG multivariate phase synchronization in early Alzheimer's disease.

Alzheimer's disease (AD) is likely to disrupt the synchronization of the bioelectrical processes in the distributed cortical networks underlying cognition. We analyze the surface topography of the multivariate phase synchronization (MPS) of multichannel EEG in 17 patients (Clinical Dementia Rating (CDR) Scale: 0.5-1; Functional Assessment Staging (FAST): 3-4) compared to 17 controls by applying a combination of global and regional MPS measures to the resting EEG. In early AD, whole-head mapping reveals a specific landscape of synchronization characterized by a decrease in MPS over the fronto-temporal region and an increase over the temporo-parieto-occipital region predominantly of the left hemisphere. These features manifest themselves through the EEG delta-beta bands and discriminate patients from controls with an accuracy of up to 94%. Moreover, the abnormal MPS in both anterior and posterior clusters correlates with the Mini Mental State Examination score, binding regional EEG synchronization to cognitive decline in AD patients. The MPS technique reveals that the EEG phenotype of early AD is relevant to the clinical picture and may ultimately become its sensitive and specific biomarker.