Biomarkers.

Area of Science:

• Neuroscience
• Gerontology
• Radiology

Background:

• The default mode network (DMN) is affected by beta-amyloid (Aβ) in early Alzheimer's Disease (AD).
• Limited data exists on how DMN functional connectivity (FC) changes across AD stages.
• This study investigates DMN FC alterations in preclinical AD.

Purpose of the Study:

• To identify characteristic DMN FC changes in preclinical AD.
• To compare DMN FC in cognitively normal (CN), mild cognitive impairment (MCI), and AD dementia groups.
• To explore the relationship between Aβ deposition and DMN FC.

Main Methods:

• 396 participants (CN, MCI, AD dementia) from the KBASE cohort (age 55-88).
• PiB PET and resting-state functional MRI were used.
• DMN FC was computed, and participants were classified by Aβ positivity (CN-, CN+, MCI+, AD+).

Main Results:

• The Aβ+ CN (CN+) group showed significantly higher within-DMN FC compared to other groups.
• The CN+ group exhibited significantly lower between-DMN FC than other groups.
• These findings indicate distinct DMN FC patterns in preclinical AD.

Conclusions:

• Increased within-DMN FC and decreased between-DMN FC are characteristic of preclinical AD.
• These DMN FC alterations may represent compensatory network activation due to early Aβ deposition.
• Further research is needed to confirm these findings and their implications for AD progression.