Dual-retrieval models and neurocognitive impairment.

Advances in dual-retrieval models of recall make it possible to use clinical data to test theoretical hypotheses about mild cognitive impairment (MCI) and Alzheimer's dementia (AD), the most common forms of neurocognitive impairment. Hypotheses about the nature of the episodic memory declines in these diseases, about decline versus sparing of specific processes, and about which individuals will become impaired over time can all be rigorously tested. Basic theoretical principles, such as whether recollection and reconstruction are distinct retrieval processes, can also be evaluated. In 3 studies, measurements of recollective retrieval, reconstructive retrieval, and familiarity judgment were extracted from standard clinical instruments, for healthy subjects and for subjects with MCI and AD diagnoses. Differences in reconstructive retrieval consistently distinguished MCI and AD, in nationally representative subject samples as well as in highly educated samples, and recollective retrieval also distinguished them in highly educated samples. Dual-retrieval processes were accurate predictors of future conversion to MCI and AD over periods of 1.5-6 years and were better predictors than the best genetic marker of these conditions (the ε4 allele of the APOE genotype). The standard recollection-deficit account of memory declines in MCI and AD was not supported, but the data were consistent with an alternative account that stresses the increasing importance of reconstruction deficits as older adults convert to these diseases.