Focal and nonfocal prospective memory performance in very mild dementia: a signature decline.

Objective: In a recent study, performance on a certain kind of prospective memory task (PM), labeled focal PM, was sensitive to the very early stages of Alzheimer's disease (AD; Duchek, Balota, & Cortese, 2006). This study sought to replicate and extend these findings by investigating both focal and nonfocal PM, as well as possible influences of alleles of the apolipoprotein E (ApoE) gene.

Method: Thirty-five healthy older adults and 33 adults in the very earliest stages of AD, as determined by the clinical dementia rating scale, completed both focal and nonfocal PM tasks. Performance on these tasks has been linked to qualitatively different cognitive processes (Scullin, McDaniel, Shelton, & Lee, 2010), thereby providing leverage to illuminate the specific processes that underlie PM failures in very early AD. Approximately half of the adults in each group were ApoE e4 carriers and half were noncarriers. We also obtained participants' scores on a battery of standard psychometric tests.

Results: There was a significant interaction between the type of PM task and dementia status, p < .05, ηp² = .12, demonstrating that the AD-related decline was more robust for focal than for nonfocal PM. Further, focal PM performance significantly discriminated between the very earliest stages of AD and normal aging, explaining variance unique to that explained by typical psychometric indices. ApoE status, however, was not associated with PM performance.

Conclusion: The pronounced deficit observed in the focal PM task suggests that spontaneous retrieval processes may be compromised in very early AD.