Memory profiling with paired associate learning in Alzheimer's disease, mild cognitive impairment, and healthy aging.

Mild cognitive impairment (MCI) is associated with increased risk of developing Alzheimer's disease (AD), but up to 40% of cases do not develop AD. Examining a case's specific memory profile may help distinguish which MCI cases will progress to AD: An encoding profile is suggestive of incipient AD, whereas a retrieval profile suggests an alternative etiology. Paired associate learning (PAL) tasks are sensitive for preclinical and early detection of AD, but existing tasks do not enable memory profiling. We developed a novel PAL task enabling the differentiation of memory profiles in 19 people with AD, 17 people with amnestic MCI, and 33 normal elderly controls. Unexpectedly, the AD group demonstrated a retrieval profile for PAL using yes-no recognition, although an encoding profile was evident for forced-choice recognition and for the California Verbal Learning Test--Second Edition (Delis, Kramer, Kaplan, & Ober, 2000). There was considerable heterogeneity within the AD and MCI groups as well as intraindividual discordance for memory profiles. The findings challenge the clinical application of memory profiling in the differential diagnosis of AD, and, by extension, question its potential application in the assessment of MCI.