Regional-based static and dynamic alterations in Alzheimer disease: a longitudinal study

Area of Science:

• Neuroscience
• Medical Imaging
• Neurology

Background:

• Alzheimer disease (AD) is characterized by cognitive decline and altered functional connectivity (FC) in critical brain regions.
• Resting-state functional magnetic resonance imaging (rs-fMRI) is used to assess these changes via static-FC and dynamic-FC analyses.

Purpose of the Study:

• To investigate region-specific functional abnormalities in Alzheimer disease (AD) longitudinally over one year.
• To evaluate the utility of static and dynamic FC approaches in identifying biomarkers for AD progression.

Main Methods:

• Analyzed data from 15 AD patients and 20 healthy controls from the Alzheimer's Disease Neuroimaging Initiative 2 (ADNI2) database.
• Participants were assessed at two time points within a one-year interval.
• Constrained-independent component analysis was employed to assess FC changes across 80 regions of interest, evaluating both static and dynamic conditions.

Main Results:

• Average regional FC decreased in AD patients compared to controls at baseline and after one year.
• Dynamic FC analysis revealed subtle differences compared to static FC analysis.
• Baseline analysis showed reduced connectivity in specific regions (e.g., right-middle-occipital/left-superior-occipital, left-hippocampus/right-postcentral). Increased connectivity was observed between left-superior-occipital and precuneus.
• One-year follow-up revealed increased connectivity in regions including right-hippocampus/left-caudate and posterior-cingulate-cortex/middle-temporal-pole.

Conclusions:

• Significant baseline FC changes were noted in frontal, occipital, and basal-ganglia regions in AD patients.
• These changes progressed towards temporal and subcortical regions over the subsequent year.
• Region-specific neurological differences identified after one year can significantly aid in AD diagnosis and disease tracking.