Spatial Navigation and APOE in Amnestic Mild Cognitive Impairment

Abstract

<i>Background:</i> The effect of APOE &#917;4 allele (&#917;4) on spatial navigation in amnestic mild cognitive impairment (aMCI) is unknown. <i>Objective:</i> Our purpose was to examine the characteristics of spatial navigation impairment in &#917;4-positive (&#917;4+) and &#917;4-negative (&#917;4–) aMCI subgroups. <i>Methods:</i> Blood samples were collected to determine the APOE genotype. A total of 34 aMCI patients were stratified into aMCI-&#917;4– (n = 23) and aMCI-&#917;4+ (n = 11) groups. Control (n = 28) and mild Alzheimer’s disease (AD; n = 16) groups were also used. We used a human analogue of the Morris water maze (enclosed arena 2.9 m in diameter) to examine body-centered (egocentric) and world-centered (allocentric) spatial navigation. <i>Results:</i> The aMCI-&#917;4+ group performed poorer on spatial navigation than the aMCI-&#917;4– group in both egocentric and allocentric tasks even though these 2 groups did not differ in global cognitive functioning or neuropsychological tests. The aMCI-&#917;4+ and mild AD groups performed similarly on all Morris Water Maze tasks and were outperformed by the aMCI-&#917;4– group, which also resembled the control group in performance on the egocentric tasks. The aMCI groups showed poor spatial navigation learning regardless of their &#917;4 positivity. <i>Conclusion:</i> We found more profound deficits in spatial navigation in aMCI-&#917;4+ relative to aMCI-&#917;4– patients. The aMCI-&#917;4+ group resembled the mild AD group in spatial navigation performance. Although the &#917;4 genotype was indicative of spatial navigation performance, it was not indicative of the aMCI patients’ ability to learn the tasks. Spatial navigation testing represents a promising area with respect to identifying individuals at higher risk for AD among the heterogeneous MCI population.