Effects of Mental Imagery on Prospective Memory: A Process Analysis in Individuals with Amnestic Mild Cognitive Impairment

Introduction: Prospective memory (PM) is a multiphasic cognitive function important for autonomy and functional independence but is easily disrupted by pathological aging processes. Through cognitive simulation of perceptual experiences, mental imagery could be an effective compensatory strategy to enhance PM performance. Nevertheless, relevant research in individuals with amnestic mild cognitive impairment (MCI) has been limited, and the underlying mechanism of the therapeutic effect has not been sufficiently elucidated. The present study aimed to examine complex PM performances and the effect of mental imagery on each phase in older adults with MCI and to investigate the underlying cognitive mechanism from a process perspective. Methods: Twenty-eight MCI and 32 normal aging controls completed a seminaturalistic PM task, in addition to a series of neuropsychological tests. Participants from each group were randomly assigned to a mental imagery condition or a standard repeated encoding condition before performing the PM task. Four indices were used to measure performance in the intention formation, intention retention, intention initiation, and intention execution phases of PM. Performances in each phase was compared between the 2 diagnostic groups and the 2 instruction conditions. Results: The MCI group performed worse than the normal aging group in the intention formation and intention retention phases. The participants in the mental imagery condition performed significantly better than those in the standard condition during the intention formation, intention retention, and intention execution phases, regardless of the diagnostic group. Moreover, there was a significant interaction between the group and condition during intention retention, showing that people with MCI benefited even more from mental imagery than normal aging in this phase. Performance in the intention retention phase predicted performance in the intention initiation and intention execution phases. Discussion: PM deficits in MCI mainly manifest during planning and retaining intentions. Mental imagery was able to promote performance in all but the initiation phase, although a trend for improvement was observed in this phase. The effects of mental imagery may be exerted in the intention retention phase by strengthening the PM cue-action bond, thereby facilitating the probability of intention initiation and bolstering fidelity to the original plan during intention execution.