Reduced neuronal efficacy in progressive mild cognitive impairment: a prospective fMRI study on visuospatial...

Area of Science:

• Neuroscience
• Cognitive Neurology
• Medical Imaging

Background:

• Mild cognitive impairment (MCI) is often a preclinical stage of Alzheimer's disease (AD).
• Neurodegenerative changes and compensatory mechanisms may precede overt clinical symptoms of AD.
• Identifying early biomarkers is crucial for timely intervention in AD progression.

Purpose of the Study:

• To investigate brain region functioning in visuospatial networks related to preclinical AD symptoms.
• To utilize event-related functional magnetic resonance imaging (fMRI) to detect alterations in MCI patients.
• To correlate brain activity with task demands and individual performance.

Main Methods:

• Prospective study of 18 MCI patients (5 progressing to AD [PMCI], 8 stable [SMCI]) and 13 controls.
• Event-related fMRI during an angle discrimination task with varying demands.
• Analysis using an extended general linear model incorporating reaction time (RT) for single trials.

Main Results:

• No significant behavioral differences (RT, accuracy) were found between MCI patients and controls.
• A bilateral activation network, including the dorsal pathway, increased linearly with task demand in all groups.
• PMCI patients exhibited a stronger task demand-brain activity relationship in the left superior parietal lobules (SPL) and increased task-independent activation in the left precuneus compared to SMCI and controls.

Conclusions:

• Altered brain function is detectable at a group level in individuals progressing to AD before behavioral changes are apparent.
• Increased parietal activation in PMCI may indicate reduced neuronal efficacy due to AD pathology.
• These findings suggest potential predictive value for future clinical decline in MCI patients.