Profiles of recent autobiographical memory retrieval in semantic dementia, behavioural-variant frontotemporal dementia, and Alzheimer's disease

Episodic autobiographical memory (ABM) comprises recollection for events that are grounded within a specific spatiotemporal context, and usually accompanied by perceptual and emotional information. The neural substrates mediating ABM retrieval are those harbouring significant pathology in semantic dementia (SD) and behavioural-variant frontotemporal dementia (bvFTD), the most common subtypes of FTD. Relatively little is known, however, regarding the differential patterns of contextual details during episodic ABM retrieval across these dementia syndromes. This study investigated episodic ABM retrieval under free and probed recall conditions from 4 time periods with the aim to identify disease-specific profiles of episodic ABM contextual details. Episodic ABM was measured in 25 SD and 15 bvFTD patients and their performance contrasted to that of 17 Alzheimer's disease (AD) patients and 19 age-matched controls. Critically, SD patients showed relatively preserved recent ABM in comparison with remote epochs. In contrast, bvFTD and AD patients showed a reduced capacity to recall specific and contextually rich ABMs across all life epochs, in both free and probed recall conditions. Analyses of the recent period (last 12 months) provided evidence for different profiles of contextual episodic details recalled in dementia syndromes. Following probing, SD patients' recall deficits emanated exclusively from compromised Emotion/Thoughts and Spatiotemporal details. In contrast, bvFTD patients were significantly impaired across all categories of contextual details whereas AD patients showed deficits for Event and Emotion/Thoughts details only. As the largest study of ABM in FTD to date, these findings emphasise the differential impairment of recent ABM contextual details contingent on the underlying disease pathology. In addition, these results point towards the importance of investigating the constituent elements of emotion processing and strategic retrieval processes as potential variables mediating recent episodic ABM retrieval.