Altered effective connectivity of the default mode network in resting-state amnestic type mild cognitive impairment

Area of Science:

• Neuroscience
• Cognitive Neurology
• Medical Imaging

Background:

• Amnestic mild cognitive impairment (aMCI) represents a critical stage between normal aging and Alzheimer's disease (AD).
• Previous research indicates impaired default mode network (DMN) functional activity in aMCI patients experiencing cognitive and memory decline.
• The specific alterations in effective connectivity within the DMN in aMCI remain incompletely understood.

Purpose of the Study:

• To investigate the dysfunctional effective connectivity within the DMN in individuals with aMCI.
• To correlate these connectivity changes with cognitive performance, particularly auditory verbal learning.
• To explore potential compensatory mechanisms within other brain networks.

Main Methods:

• Utilized independent component analysis (ICA) combined with multivariate Granger causality analysis (mGCA).
• Analyzed resting-state fMRI data from 18 aMCI patients and 18 age-matched healthy controls.
• Assessed effective connectivity between key DMN regions, including the middle temporal gyrus (MTG), hippocampus (HC), fusiform gyrus (FG), and precuneus/posterior cingulate cortex (PreCN/PCC).

Main Results:

• Demonstrated decreased effective connectivity between MTG, HC, and FG, and between PreCN/PCC and HC in aMCI patients.
• Found a significant correlation between impaired DMN connectivity and poorer auditory verbal learning performance.
• Observed enhanced effective connectivity within the frontal cortex in aMCI patients.

Conclusions:

• Findings elucidate the specific patterns of dysfunctional DMN connectivity in aMCI.
• Highlight the role of altered effective connectivity in the pathophysiology of aMCI.
• Suggest that enhanced frontal connectivity may represent a compensatory mechanism for memory deficits in aMCI.