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Differential prospective memory profiles in frontotemporal dementia syndromes.

BACKGROUND
Prospective memory (PM) is the ability to remember to execute an intended action either at a future time (Time-based PM) or when a specific event occurs (Event-based PM). Previous studies demonstrate impaired PM in Alzheimer's disease (AD); however, the status of PM in frontotemporal dementia (FTD) remains unknown.


OBJECTIVE
To examine PM performance and its associated cognitive mechanisms, in two subtypes of FTD: semantic dementia (SD) and the behavioral variant of FTD (bvFTD), in comparison with matched AD and control participants.


METHODS
Twenty-four dementia patients (SD = 8; bvFTD = 8; AD = 8) and 12 age- and education-matched controls underwent a shortened version of the Cambridge Behavioural Prospective Memory Test, as well as a standard neuropsychological test battery.


RESULTS
Compared to controls, SD patients exhibited preserved Time-based PM in the context of impaired Event-based PM, with the latter strongly associated with deficits in semantic processing. In contrast, bvFTD and AD patients demonstrated global PM impairments irrespective of subscale, which strongly correlated with deficits in delayed episodic retrieval for both groups. Caregiver reports of stereotypical behaviors were associated with compromised Event-based PM in SD and Time-based PM in bvFTD, with no such relationship evident in AD.


CONCLUSION
This is the first study to investigate prospective memory in FTD syndromes. A relative sparing of Time-based PM was observed in SD, in contrast with global PM deficits in bvFTD. Disrupted PM processing was found to correlate with stereotypical behaviors in FTD syndromes, a finding that we suggest is worthy of further investigation.