| Summary: | The research presented in this thesis is a clinical and experimental investigation of dysgraphia in patients with either the temporal variant of frontotemporal dementia, or dementia of the Alzheimer's type (DAT). The first empirical chapter describes a longitudinal case study of two patients with temporal-lobe atrophy who had a similar progressive dysgraphia syndrome. At presentation, SC and FM exhibited (central) surface dysgraphia on both oral and written spelling, but on follow-up there was a gradual emergence of nonphonologically plausible spelling errors. An additional peripheral dysgraphia in both cases consisted of difficulty with producing letters, particularly in lower case, without a model to copy. Examination of a further 28 dysgraphic patients with cortical dementia revealed a strong concordance between spelling and letter production problems. It is argued that these deficits are meaningfully associated, and that damage to an interactive system with word- and letter-based levels of representation could plausibly account for these results. The second empirical chapter describes a long-term follow-up study of FM, who developed "jargon dysgraphia": in writing to dictation, she fluently produced well-formed written output consisting of pronounceable neologisms which, over time, bore a progressively weaker resemblance to the target words. Ultimately, FM's spelling responses had no detectable similarity with the targets, although they remained word-like. The pattern of performance could be explained by more extreme degradation in orthographic representations, or by isolation of the orthographic system from semantics and phonology.
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