Alzheimer’s Disease and Brain Hubs: Exploring Resting-State Alpha Rhythms

Published on January 26, 2023

Imagine your brain as a network made up of nodes and connections. In a study, researchers compared the brain hubs of normal elderly individuals and those with Alzheimer’s disease dementia. They focused on the resting-state alpha rhythms, which are associated with abnormal brain activity in Alzheimer’s. The results showed that both groups had significant parietal hubs, or central regions, connected to other clusters of nodes. However, the ‘directionality’ of these hubs was lower in Alzheimer’s patients compared to the healthy participants. This suggests that there might be a disruption in the flow or communication of information in the brains of Alzheimer’s patients. Additional studies could explore how this decreased ‘directionality’ relates to cognitive decline and potential therapeutic interventions. Fascinating research demonstrating the complexities of Alzheimer’s disease and how analyzing brain networks can provide valuable insights!

IntroductionGraph theory models a network by its nodes (the fundamental unit by which graphs are formed) and connections. ‘Degree’ hubs reflect node centrality (the connection rate), while ‘connector’ hubs are those linked to several clusters of nodes (mainly long-range connections).MethodsHere, we compared hubs modeled from measures of interdependencies of between-electrode resting-state eyes-closed electroencephalography (rsEEG) rhythms in normal elderly (Nold) and Alzheimer’s disease dementia (ADD) participants. At least 5 min of rsEEG was recorded and analyzed. As ADD is considered a ‘network disease’ and is typically associated with abnormal rsEEG delta (<4 Hz) and alpha rhythms (8–12 Hz) over associative posterior areas, we tested the hypothesis of abnormal posterior hubs from measures of interdependencies of rsEEG rhythms from delta to gamma bands (2–40 Hz) using eLORETA bivariate and multivariate-directional techniques in ADD participants versus Nold participants. Three different definitions of ‘connector’ hub were used.ResultsConvergent results showed that in both the Nold and ADD groups there were significant parietal ‘degree’ and ‘connector’ hubs derived from alpha rhythms. These hubs had a prominent outward ‘directionality’ in the two groups, but that ‘directionality’ was lower in ADD participants than in Nold participants.DiscussionIn conclusion, independent methodologies and hub definitions suggest that ADD patients may be characterized by low outward ‘directionality’ of partially preserved parietal ‘degree’ and ‘connector’ hubs derived from rsEEG alpha rhythms.

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