EEG coherence as a marker of Alzheimer's disease

BackgroundProgressive deterioration of synaptic plasticity and synaptic connectivity between neurons is a neurophysiological hallmark of brain ageing and has been linked to the severity of dementia. We hypothesized that if synaptic disconnection as the neuropathology of Alzheimers disease (AD) is responsible for the failure of the brain to integrate various regions into effective networks, then electroencephalographic evidence of the disruption of functional connectivity might be used to diagnose Alzheimers dementia. We proposed that changes in EEG coherence, a measure of functional interaction between the brain collaborating areas, can be detected in a clinical setting and serve as a marker of neuronal disconnection. Improving the accuracy and reducing the time needed to diagnose AD could allow timely interventions, treatments, and care cost reduction. MethodsThis study examined group differences in EEG coherence within global cortical networks at rest and during executive challenges among patients with AD, individuals with mild cognitive impairment, and healthy controls. ResultsDecreased EEG coherence has been discovered in cross-hemisphere frontal, temporal, parietal and occipital pairs in the AD group at rest and when challenged with tasks requiring comprehension, analysis, perceptual-motor response, and executive functioning. The most notable changes were detected in F3-F4 Beta with the visual-spatial task challenge, P7-P8 Beta during the writing task, T7-T8 Gamma during a task requiring speech understanding and O1-O2 Alpha during orientation in space task. ConclusionsThe study identified several potential EEG biomarkers of AD. More research is needed to identify sensitivity and specificity of the markers.