Memory for intentions in amnestic mild cognitive impairment: time- and event-based prospective memory.

Amnestic mild cognitive impairment (aMCI) is associated with neuropathological changes in medial-temporal and frontal-system structures. By definition, retrospective memory is mildly impaired in aMCI. We examined whether prospective memory (PM) is also impaired, in particular time-based PM, which requires considerable self-initiation and inhibition. We administered time- and event-based PM tasks to 42 healthy older adults, 45 individuals with aMCI, and 24 individuals with Alzheimer's disease (AD). The healthy group performed better than the aMCI group, and the aMCI group performed better than the AD group on both PM tasks. Importantly, the aMCI group performed more poorly on the time- than event-based task, whereas the other groups performed comparably on both tasks. Findings suggest that PM, particularly time-based PM, is sensitive to the earliest cognitive changes associated with aMCI, possibly reflecting decreased self-initiation, attention switching, and/or inhibition on memory tasks because of early involvement of the frontal system.