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.

Famous faces and voices: Differential profiles in early right and left semantic dementia and in Alzheimer's disease.

BACKGROUND: Famous face and voice recognition is reported to be impaired both in semantic dementia (SD) and in Alzheimer's Disease (AD), although more severely in the former. In AD a coexistence of perceptual impairment in face and voice processing has also been reported and this could contribute to the altered performance in complex semantic tasks. On the other hand, in SD both face and voice recognition disorders could be related to the prevalence of atrophy in the right temporal lobe (RTL). OBJECTIVE: The aim of the present study was twofold: (1) to investigate famous faces and voices recognition in SD and AD to verify if the two diseases show a differential pattern of impairment, resulting from disruption of different cognitive mechanisms; (2) to check if face and voice recognition disorders prevail in patients with atrophy mainly affecting the RTL. MATERIALS: To avoid the potential influence of primary perceptual problems in face and voice recognition, a pool of patients suffering from early SD and AD were administered a detailed set of tests exploring face and voice perception. Thirteen SD (8 with prevalence of right and 5 with prevalence of left temporal atrophy) and 25 CE patients, who did not show visual and auditory perceptual impairment, were finally selected and were administered an experimental battery exploring famous face and voice recognition and naming. Twelve SD patients underwent cerebral PET imaging and were classified in right and left SD according to the onset modality and to the prevalent decrease in FDG uptake in right or left temporal lobe respectively. Correlation of PET imaging and famous face and voice recognition was performed. RESULTS: Results showed a differential performance profile in the two diseases, because AD patients were significantly impaired in the naming tests, but showed preserved recognition, whereas SD patients were profoundly impaired both in naming and in recognition of famous faces and voices. Furthermore, face and voice recognition disorders prevailed in SD patients with RTL atrophy, who also showed a conceptual impairment on the Pyramids and Palm Trees test more important in the pictorial than in the verbal modality. Finally, in 12SD patients in whom PET was available, a strong correlation between FDG uptake and face-to-name and voice-to-name matching data was found in the right but not in the left temporal lobe. DISCUSSION: The data support the hypothesis of a different cognitive basis for impairment of face and voice recognition in the two dementias and suggest that the pattern of impairment in SD may be due to a loss of semantic representations, while a defect of semantic control, with impaired naming and preserved recognition might be hypothesized in AD. Furthermore, the correlation between face and voice recognition disorders and RTL damage are consistent with the hypothesis assuming that in the RTL person-specific knowledge may be mainly based upon non-verbal representations.