Spatial pattern separation differences in older adult carriers and non-carriers for the apolipoprotein E epsilon 4 allele

• Examined performance of young and older adults on a spatial pattern separation task.
• Older adults were genotyped as apolipoprotein E-ε4 carriers or non-carriers.
• ε4 carriers classified as impaired or unimpaired using a standardized memory test.
• Older ε4 carriers in impaired group displayed spatial pattern separation deficits.
• Pattern separation may be less efficient in ε4 carriers with subtle memory decline.

We examined the performance of healthy young (n = 57) and older adults (n = 43) genotyped as apolipoprotein E-ε4 (APOE-ε4) carriers or APOE-ε4 non-carriers on a delayed match-to-sample task involving varying degrees of spatial interference hypothesized to assess spatial pattern separation. Older adult ε4 carriers were further divided into “impaired” and “unimpaired” groups based on their performance on a standardized test of verbal memory. We found that performance on the spatial pattern separation test increased as a function of decreased spatial interference across all groups. The older ε4 carriers in the impaired group performed significantly worse (p < .05) than unimpaired ε4 carriers, ε4 non-carriers, and young adults. The data suggest that spatial pattern separation may be less efficient in a subset of healthy older adults with subtle memory decline who are carriers of the ε4 allele. However, pattern separation performance may be comparable to that of young adults in a subset of older adult ε4 carriers and more broadly among non-carriers. Our findings offer additional evidence that pattern separation may vary in older adults, and they provide novel insight into pattern separation efficiency in ε4-positive older adults.