Prospective memory impairments in Alzheimer's disease and behavioral variant frontotemporal dementia: Clinical and neural correlates

Background: Prospective memory (PM) refers to a future-oriented form of memory in which the individual must remember to execute an intended action either at a future point in time (Time-based) or in response to a specific event (Event-based). Lapses in PM are commonly exhibited in neurodegenerative disorders including Alzheimer's disease (AD) and frontotemporal dementia (FTD), however, the neurocognitive mechanisms driving these deficits remain unknown. Objective: To investigate the clinical and neural correlates of Time- and Event-based PM disruption in AD and the behavioralvariant FTD (bvFTD). Methods: Twelve AD, 12 bvFTD, and 12 healthy older Control participants completed a modified version of the Cambridge Prospective Memory test, which examines Time- and Event-based aspects of PM. All participants completed a standard neuropsychological assessment and underwent whole-brain structural MRI. Results:ADand bvFTD patients displayed striking impairments across Time- and Event-basedPMrelative to Controls, however, Time-based PM was disproportionately affected in the AD group. Episodic memory dysfunction and hippocampal atrophy were found to correlate strongly with PM integrity in both patient groups, however, dissociable neural substrates were also evident for PM performance across dementia syndromes. Conclusion: Our study reveals the multifaceted nature of PM dysfunction in neurodegenerative disorders, and suggests common and dissociable neurocognitive mechanisms, which subtend these deficits in each patient group. Future studies ofPMdisturbance in dementia syndromes will be crucial for the development of successful interventions to improve functional independence in the patient's daily life.