Hippocampus-based static functional connectivity mapping within white matter in mild cognitive impairment

Area of Science:

• Neuroscience
• Radiology
• Gerontology

Background:

• Mild cognitive impairment (MCI) is linked to memory loss and hippocampal atrophy.
• White matter (WM) signal changes are observed in MCI using resting-state functional MRI (fMRI).
• The precise impact of hippocampal dysfunction on WM in MCI remains unclear.

Purpose of the Study:

• To investigate functional connectivity (FC) alterations between the hippocampus and other brain regions in MCI and very mild cognitive impairment (VMCI).
• To explore the relationship between abnormal FC and structural connectivity disruptions in WM.
• To identify potential imaging biomarkers for memory decline in Alzheimer's disease progression.

Main Methods:

• Utilized resting-state fMRI data from 43 MCI, 71 VMCI, and 87 healthy controls (HCs) from the OASIS-3 dataset.
• Analyzed whole-brain FC maps using the hippocampus as seed regions.
• Employed one-way ANOVA for group comparisons and probabilistic tracking for structural connectivity assessment.

Main Results:

• MCI and VMCI groups showed reduced FC in specific gray and white matter regions compared to HCs.
• Dysconnectivity was observed in the cerebellum, temporal lobe, and frontal lobe.
• Increased mean diffusivity in WM fiber bundles connecting the hippocampus and temporal pole was found in MCI patients.

Conclusions:

• Hippocampal activity abnormalities significantly affect white matter functional and structural connectivity in MCI.
• These findings suggest novel functional imaging approaches for understanding memory decline in Alzheimer's disease.
• The study highlights specific connectivity disruptions as potential indicators of MCI progression.