Recognition Memory in Amnestic Mild Cognitive Impairment
Ullrich, Lauren Elizabeth
A detailed characterization of the memory impairment in amnestic mild cognitive impairment (aMCI) is important both clinically and in the interests of research. The progressive nature of dementia and the fact that neuronal loss often precedes behavioral symptoms means that early detection of Alzheimer's disease will be crucial for any preventative strategy. In addition, because memory loss occurs in tandem with medial temporal lobe degeneration, studies of this population can provide insight into the nature of the brain structures underlying recognition memory. The current study investigated memory impairment in aMCI through a dual-process framework, which holds that recognition memory is supported by two processes: recollection and familiarity. While familiarity has generally been found to be preserved in healthy aging, there is some evidence that this process may be impaired in aMCI, though reports have been inconsistent. In the current study, participants with aMCI and age-and education-matched controls were tested on the remember-know task, the confidence judgment procedure, and the process dissociation procedure. On all three tasks, aMCI participants demonstrated impairment in both recollection and familiarity. Additionally, these processes were correlated with the volumes of four MTL structures: the hippocampus and the entorhinal, perirhinal, and posterior parahippocampal cortices. Consistent with the dual-process model, across aMCI and control participants, the strongest relationships were between recollection and hippocampal volume and familiarity and entorhinal cortex volume. The results from this study suggest that measures of familiarity, in particular, may have utility as a proxy for AD neuropathology, but the predictive value of this measure still requires additional study.
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