State-based functional connectivity changes associate with cognitive decline in amnestic mild cognitive impairment...

Area of Science:

• Neuroscience
• Cognitive Neurology
• Neuroimaging

Background:

• Episodic memory (EM) dysfunction is a hallmark of amnestic mild cognitive impairment (aMCI), a condition with high conversion risk to Alzheimer's disease (AD).
• The modulation of the EM network during situational switching in aMCI remains poorly understood.

Purpose of the Study:

• To investigate functional connectivity (FC) alterations within the EM network in aMCI subjects compared to cognitively normal (CN) individuals.
• To examine how the EM network reconfigures from a resting-state to an episodic memory retrieval task-state.
• To identify correlations between EM network connectivity and cognitive performance in aMCI.

Main Methods:

• Recruited 26 aMCI and 22 CN subjects for multi-dimensional neuropsychological tests and resting-state/task-state functional magnetic resonance imaging (fMRI).
• Constructed the EM network using a seed-based FC approach, focusing on connectivity changes between resting and task states.
• Analyzed differences in FC between aMCI and CN groups and correlated connectivity strength with cognitive scores.

Main Results:

• AMCI subjects exhibited poorer performance in episodic memory and executive function compared to CN subjects.
• Significantly decreased connectivity was observed in aMCI subjects between the left posterior parahippocampal gyrus (LpPHG) and the left ventral medial prefrontal cortex and right postcentral gyrus (RPCG).
• Across all subjects, increased connectivity of LpPHG to the right dorsal medial prefrontal cortex (RDMPFC), RPCG, left inferior parietal cortex, and bilateral superior parietal lobe occurred during the task-state compared to resting-state. Changed LpPHG-RDMPFC connectivity correlated with EM and executive function scores in aMCI.

Conclusions:

• General brain regions are functionally organized and integrated into the EM network, mobilizing cognitive resources to meet task demands.
• Findings suggest altered functional organization and integration within the EM network in aMCI.
• These results enhance understanding of the neural mechanisms underlying EM deficits in aMCI.