A Winding Road: Alzheimer's Disease Increases Circuitous Functional Connectivity Pathways.

Area of Science:

• Neuroimaging
• Neuroscience
• Medical Imaging

Background:

• Alzheimer's disease (AD) is characterized by cerebral atrophy.
• Functional connectivity analysis of brain signals is emerging for AD research.
• Current methods often overlook weaker brain connections.

Purpose of the Study:

• To investigate functional connectivity in mild-to-moderate Alzheimer's disease (AD).
• To compare brain connectivity patterns between AD patients and controls.
• To explore the impact of including all connection strengths, including weaker ones, in the analysis.

Main Methods:

• Used blood-oxygen-level dependent (BOLD) functional MRI during resting wakefulness.
• Included all positive functional connectivities, regardless of strength.
• Calculated transitive closures to classify connections as direct or indirect.
• Compared patients with mild-to-moderate AD (N=11) and controls (N=12).

Main Results:

• Observed significant differences in the proportion of indirect brain pathways between AD patients and controls.
• Found broadly increased indirect connectivity across greater spatial distances in AD.
• Demonstrated greater between-subject topological variance in indirect pathways for AD patients.

Conclusions:

• The characterization of AD as a disconnection syndrome is refined.
• Increased indirect functional pathways may compensate for impaired direct links in AD.
• Analyzing the full spectrum of connection strengths is crucial for detecting subtle AD-related brain changes.