Acalculia: Deficits of operational and quantity number knowledge

We describe the standardization of three new tests of knowledge of quantity facts, number operations and multiplication facts. We also report a validation study in which a group of 50 patients with cortical degenerative disorders were tested on these three new tests of number processing. Our results show that the quantity facts and number operations tests are sensitive measures of number processing abilities. Performance on the three new tests and the Graded Difficulty Arithmetic (GDA) test were found to be significantly impaired in the Alzheimer's Disease (AD) group. The frontotemporal dementia (FTD) group was subdivided into those with a semantic dementia (SD) and those with prominent frontal features (Non-SD). The semantic dementia subgroup was more impaired than both the AD patient group and the nonsemantic FTD subgroup on the quantity facts test. A more fine grained analysis reveals several interesting patterns of performance, including a dissociation between impaired performance on the quantity facts and number operations tests and preserved performance on the GDA. The findings attest the value of comparing performance on the GDA and our new tests in delineating the nature of an individual's number processing deficits. Implications for the relation between simple arithmetic fact knowledge and higher level number processing are discussed.