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P2‐201: Local and distal coherence as a measure of cortical connectivity in Alzheimer's disease
Author(s) -
Sankari Ziad T.
Publication year - 2010
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2010.05.1250
Subject(s) - neuroscience , coherence (philosophical gambling strategy) , electroencephalography , psychology , physics , quantum mechanics
Background: Alzheimer’s disease (AD) is characterized by three major markers: histological formation of microscopic amyloid plaques and neurofibrillary tangles in the brain, and the loss of connections between neurons. While microscopic plaques and tangles remain undetectable by modern imaging techniques, Electroencephalograms (EEGs) offer a powerful alternative solution with high spatial and temporal resolution to glean insights into brain’s cortical connectivity and other potential markers of AD. This research presents a comprehensive EEG study for local and distal cortical connectivity in AD patients as measured by coherence. Methods: Coherence is the magnitude squared of the cross-spectrum of two signals divided by the product of the power spectral densities (PSD) of each of the signals. In this research, EEGs are obtained from 20 AD probable patients and 7 healthy controls. Pair-wise electrode coherence is calculated over each frequency band (delta, theta, alpha and beta). One-way ANOVA test shows a set of statistically significant differences in electrode coherence between AD and controls. Results: AD patients present a significant pattern of increase in the left temporo-parietal coherence in the delta, theta and alpha bands, and a decrease in the right temporo-parietal coherence in all bands. Decrease in coherence of AD patients is often attributed to a decrease in cholinergic connectivity along pathways connecting temporal, occipital and parietal areas with the frontal region of the brain. On the other hand, the increase in temporo-parietal, temporo-central and frontal coherence of AD patients in specific bands, being most pronounced in the theta band, could be attributed to compensatory mechanisms that attempt to make up for the decrease in memory and cognitive functions caused by the progression of AD. Moreover, this research shows that AD patients exhibit a change in the distal coherence pattern observed in healthy subjects. A possible explanation may be the loss of distal axonal connections as amyloid plaques and neurofibrillary tangles form in AD patients blocking the flow of electric signals between the far sides of the brain. Conclusions: This research demonstrates that AD patients show signicant changes in cortical connectivity compared to controls. It suggests that coherence studies have potentials in differentiating between healthy elderly and probable AD patients.