Altered functional connectivity between primary visual cortex and cerebellum in Alzheimer's disease

Area of Science:

• Neuroimaging
• Neuroscience
• Medical Imaging

Background:

• Eyes-open (EO) and eyes-closed (EC) states differentially organize brain networks in healthy individuals.
• Functional connectivity (FC) analysis using resting-state fMRI under EO/EC conditions is used to study Alzheimer's disease (AD).
• The influence of eye conditions on FC across the AD continuum is not well-established.

Purpose of the Study:

• To investigate the impact of eye conditions (EO vs. EC) on functional connectivity (FC) throughout the Alzheimer's disease (AD) continuum.
• To explore how FC patterns differ between EO and EC states in cognitively normal (CN) and mild cognitive impairment (MCI) individuals with and without amyloid-beta (Aβ) pathology, as well as in AD patients.

Main Methods:

• Functional connectivity (FC) was assessed using a primary visual cortex (V1) seed in individuals across the AD continuum (CN-, CN+, MCI+, AD).
• Data were collected under both eyes-open (EO) and eyes-closed (EC) conditions.
• Participants included 59 Aβ-PET negative CN, 14 Aβ-PET positive CN, 24 MCI+, and 15 AD individuals.

Main Results:

• Both EO and EC conditions modulated FC between the V1 and cerebellum (posterior vermis) across all groups.
• EO facilitated V1-cerebellum FC more than EC in CN-, CN+, and MCI+ groups.
• The AD group exhibited the opposite pattern, with EC showing greater V1-cerebellum FC than EO. FC correlated with truncal balance under EO in MCI+ and AD groups.

Conclusions:

• Functional connectivity (FC) between the visual cortex (V1) and cerebellum is altered in Alzheimer's disease (AD).
• These V1-cerebellum connectivity changes may contribute to impaired truncal balance and falls in AD patients.
• Analyzing FC under both EO and EC conditions could offer a novel functional biomarker for AD detection and monitoring.