Arithmetic knowledge in early semantic dementia.

The issue of whether arithmetic knowledge is invariably spared or impaired in semantic dementia is still under debate. The corpus of data mainly relies on single case-report descriptions. Relative to this issue, only one paper, by Julien et al. (Neuropsychologia 44(10): 2732-2744, 2008) explored in a systematic way arithmetic knowledge in an SD patient group. The present study is aimed to explore calculation in a group of eight patients affected by early semantic dementia (SD) using a neuropsychological battery devised to examine arithmetic knowledge (arithmetic signs recognition, arithmetic facts and written and mental calculation). These SD patients showed problems in recognition of arithmetic signs, difficulty in arithmetic facts and procedural errors in calculation. Still, the pattern of answers that the SD patients showed was not completely homogeneous and some individual variations were present. In contrast with most literature, the present study provides evidence for impairment of arithmetic knowledge in patients with early semantic dementia and contributes to the recent evidence that arithmetic knowledge cannot be considered an independent domain within the semantic system.