Functional connectivity changes differ in early and late-onset Alzheimer's disease

Area of Science:

• Neuroscience
• Neurology
• Medical Imaging

Background:

• Early-onset Alzheimer's disease (EOAD) and late-onset Alzheimer's disease (LOAD) present with differing patterns of brain atrophy and dysfunction.
• The distinct organization of neural networks in EOAD versus LOAD remains largely uninvestigated.

Purpose of the Study:

• To characterize and compare basal functional connectivity (FC) patterns in the default mode network (DMN), anterior temporal network (ATN), and dorso-lateral prefrontal network (DLPFN) between EOAD and LOAD patients.
• To investigate the relationship between FC patterns and cognitive performance in these patient groups.

Main Methods:

• Magnetic resonance imaging (MRI) was used to assess brain atrophy and resting-state functional connectivity (FC).
• Neuropsychological assessments were conducted on 14 EOAD patients, 14 LOAD patients (matched for disease duration and severity), and age-matched controls.

Main Results:

• Both EOAD and LOAD showed decreased FC within the DMN compared to controls.
• A double-dissociation was observed in other networks: EOAD exhibited decreased FC in the DLPFN and increased FC in the ATN, while LOAD showed the reverse pattern.
• FC in the ATN and DLPFN correlated with memory and executive functions, respectively, suggesting compensatory mechanisms.

Conclusions:

• Alzheimer's disease presents with both common and distinct large-scale neural network alterations in its early-onset and late-onset forms.
• These differences in network organization likely stem from variations in the distribution of pathological changes.