Event-based prospective memory failure in amnestic mild cognitive impairment

Prospective memory (PM) deficits have recently been documented in individuals with amnestic mild cognitive impairment (aMCI). In this paper, we investigated whether these deficits are due to the failure of retrospective memory processes. We also examined the role played by attentional/executive processes in PM functioning. We enrolled 24 individuals with aMCI and 24 healthy controls (NCs). In the PM procedure, we manipulated both the memory load of the retrospective component of the PM task and the complexity of the ongoing task in a 2 × 2 experimental design. Sequences of four words were presented. Participants had to repeat the sequence in the same order (low attentional demand condition) or in the reverse order (high attentional demand condition). When a target word appeared in the sequence, participants had to press a button on the keyboard (PM task). Target words could be one (low memory load condition) or four (high memory load condition) in different blocks. MCI participants obtained lower PM scores than NCs in all four experimental conditions. However, they recalled the target words less accurately than NCs only in one four-word condition. Finally, the executive demand of the ongoing task did not significantly affect the PM performance of aMCI individuals. Our findings confirm that PM is severely impaired in individuals with aMCI. Moreover, a failure of retrospective memory processes does not seem to fully account for the poor PM performance in aMCI individuals. Finally, the finding that in these individuals, a deficit in executive control cannot be claimed as the main responsible for the observed PM impairment could suggest the involvement of automatic-reflexive processes.