Prospective Memory Abilities In Aging and Mild Cognitive Impairment/ Early Alzheimer’s Disease

Abstract

This dissertation describes separate but related studies that explore the prospective memory abilities of older adults and individuals with Mild Cognitive Impairment/Early Alzheimer’s disease. Prospective memory (PM) refers to the type of memory utilized to execute planned actions in accordance with a specific event. PM is critical to maintaining functional independence in older adults, as it can refer to such basic acts as remembering to turn off a stove or taking one’s medication. Research suggests PM abilities decline within normal aging and to a greater extent in Mild Cognitive Impairment (MCI) and early Alzheimer’s Disease (AD). Together, the studies assessed and compared the PM abilities across healthy younger and older adults, individuals with MCI, and individuals with early AD while exploring two major theories that seek to explain PM retrieval. The preparatory attentional and memory process theory of PM (PAM) assumes that PM retrieval requires resource-demanding preparatory attentional processes, whereas the Dynamic Multiprocess theory (DMPT) assumes that retrieval can also occur spontaneously (Scullin, McDaniel, & Shelton, 2013; Smith & Bayen, 2006). Study 1 used a novel laboratory PM task in which the focality and the frequency of PM cues were manipulated to compare the PM abilities of cognitively healthy younger and older adults. The results revealed significant differences in the patterns of performance between the younger and older adults based on the focality and frequency of cues which indicated different attentional allocation strategies. Study 2 examined the impact of cognitive impairment on PM abilities by using the same paradigm to compare the performance of cognitively healthy older adults to individuals with MCI and early AD. The results again revealed significant differences in the patterns of performance which indicated that these groups may have used different strategies of attentional allocation depending on the focality and cue frequency. Taken together, the findings in Studies 1 and 2 were mixed with respect to the predictions of the DMPT and PAM. The MCI group, in particular, demonstrated a unique performance profile that suggests the neuropathophysiological changes associated with this diagnosis may lead to the reliance on different PM retrieval processes compared to healthy older adults. Finally, Study 3 explored the use of a more naturalistic and ecologically valid PM task to compare the PM performance of individuals with MCI and early AD to healthy older adults without cognitive impairment. The results showed that, after taking the learning and retrospective memory scores into account, the significant differences between groups in PM accuracy on this task can mostly be accounted for by these factors. Nevertheless, the AD group was found to display significantly lower PM accuracy with event-based cues with a weak association between cue and action compared to the older adult and MCI groups after controlling for these factors. These findings provide valuable theoretical, methodological, and clinical contributions which will be discussed.