Activity in Memory Brain Networks During Encoding Differentiates Mild Cognitive Impairment Converters from...

Area of Science:

• Neuroscience
• Medical Imaging
• Cognitive Science

Background:

• Alzheimer's disease (AD) is linked to memory deficits, particularly affecting the medial temporal lobe (MTL) and precuneus.
• Understanding brain network alterations in early stages like mild cognitive impairment (MCI) is crucial for early diagnosis and intervention.

Purpose of the Study:

• To investigate the impact of Alzheimer's disease on brain networks involving the hippocampus and precuneus during memory encoding.
• To explore potential differences in network activation between MCI converters (MCIc), MCI non-converters (MCIn), and AD patients.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used during a memory encoding task in 68 MCI patients, 21 AD patients, and 20 healthy controls (HC).
• Independent component analysis (ICA) was applied to analyze brain networks associated with the MTL and precuneus.
• MCI patients were clinically followed for 18 months to determine conversion status.

Main Results:

• Healthy controls outperformed MCI converters and AD patients in memory tasks.
• MCI converters exhibited significantly higher activation in the MTL-associated network (including hippocampus, parahippocampus, fusiform gyrus) compared to MCIn and AD patients.
• The precuneus network, linked to the default mode network, showed a negative correlation with behavioral performance.

Conclusions:

• Hyperactivation in the hippocampal network among MCI converters may serve as a compensatory mechanism.
• This heightened activation has potential diagnostic value for differentiating MCI converters from non-converters.
• The findings offer insights into early brain changes associated with Alzheimer's disease progression.