APOE and spatial navigation in amnestic MCI: results from a computer-based test.

Area of Science:

• Neuroscience
• Genetics
• Cognitive Science

Background:

• Apolipoprotein E (APOE) ε4 allele is a significant genetic risk factor for Alzheimer's disease and cognitive decline.
• Spatial navigation deficits are an early sign of cognitive impairment, often preceding memory loss.
• The hippocampus plays a crucial role in spatial memory and navigation.

Purpose of the Study:

• To investigate the association between APOE ε4 genotype and spatial navigation performance in patients with amnestic mild cognitive impairment (aMCI).
• To determine if hippocampal volume mediates the relationship between APOE ε4 status and spatial navigation deficits.
• To assess the dose-dependent effect of APOE ε4 carriage on spatial navigation.

Main Methods:

• Seventy-four patients with aMCI were categorized based on APOE ε4 carrier status (noncarriers, heterozygotes, homozygotes).
• Spatial navigation was assessed using a computerized Morris Water Maze analogue, measuring egocentric and allocentric navigation.
• Brain MRI was performed to quantify hippocampal volume using automated volumetry.

Main Results:

• APOE ε4 carriers exhibited significantly poorer performance on all spatial navigation tasks compared to noncarriers, irrespective of neuropsychological profile.
• A dose-dependent effect was observed, with APOE ε4 homozygotes performing worse than heterozygotes.
• Reduced right hippocampal volume was associated with poorer allocentric and delayed spatial navigation, but not egocentric navigation.

Conclusions:

• Spatial navigation deficits in aMCI worsen in a dose-dependent manner with increasing APOE ε4 gene dosage.
• These navigation impairments are, at least partially, explained by differences in right hippocampal volume.
• A computer-based tool effectively identified spatial navigation deficits related to APOE ε4 status in aMCI.