The neuropsychology of frontal variant frontotemporal dementia and semantic dementia. Introduction to the special topic papers: Part II.

The second part of this review, which accompanies 10 special topic articles dedicated to frontotemporal dementia (FTD), describes some of the advances in understanding frontal variant FTD (fvFTD) and semantic dementia, and the theoretical insights gained into normal cognitive processes from the study of these syndromes. Recent work has clarified the neuropsychiatric features that distinguish fvFTD from Alzheimer's and has begun to spread light on the underlying deficits in social judgement, theory of mind, processing of emotional stimuli and decision making. With regard to central aspects of cognitive processing, such as memory, patients with fvFTD may have a distinctive profile of performance on tests of explicit and implicit memory, and contrary to current views some patients may even have a severe amnesic syndrome. There is also growing evidence that despite relatively well preserved general language skills, patients with fvFTD have particular problems with verb processing. Although there is agreement regarding the key features of semantic dementia, much controversy has surrounded the issue of whether the cognitive findings favour an explanation in terms of progressive breakdown of a central amodal semantic store or differential involvement of verbal and non-verbal systems. Other topics discussed include the impact of semantic breakdown on phonological processes and episodic memory. We also review recent structural and functional neuroimaging findings in semantic dementia.