Characteristics of Associative Memory Deficits in Amnestic Mild Cognitive Impairment

Abstract

Amnestic mild cognitive impairment (aMCI) patients show impairment in both item and associative memory. The current study administered the widely used associative and item memory tests from the Clinical Memory Scale to investigate whether aMCI patients are more impaired in associative memory than item memory. In addition, we aimed to analyze an associative memory test (the paired-associate learning test) in order to investigate in detail the nature of associative memory impairment in aMCI patients. Twenty-five individuals with aMCI and 28 healthy controls took part in the study. Two associative memory tests (paired-associate learning test and associative recall), two item memory tests (free recall of pictures and recognition of meaningless figures), and a set of neurocognitive tests were administered to the participants. aMCI patients performed significantly worse than healthy older adults in both associative memory tests, even when controlling for impairment in the item memory tests. In addition, ROC curve analysis indicated that discriminative power was higher in associative than in item memory tests. Further, the results of the paired-associate learning test indicated that, compared to normal older adults, aMCI patients showed more deficits in remembering the easy word pairs, relative to the difficult word pairs. Our results confirm that aMCI patients demonstrate greater deficits in associative memory than in item memory. In addition to the impairment in creating memory links between items, aMCI patients may have deficits in using the semantic information presented by the items. The associative memory tests showed higher discriminative power than item memory tests in the identification of aMCI patients. Including associative memory testing in future neurocognitive assessment protocols could be helpful to improve the hit rate of aMCI detection.