Impaired arithmetic facts but intact conceptual knowledge--a single-case study of dyscalculia.

We present the case of a young, highly educated patient who showed severe problems in basic arithmetic after a bone marrow transplant followed by extensive irradiation and chemotherapy. Despite his inability to resolve arithmetical fact problems (as 2 + 3), he showed intact processing of algebraic expressions and excellent understanding of complex arithmetic text problems. He perfectly knew arithmetic principles and applied them in various tasks. The performance of the patient suggests that conceptual knowledge (in addition to arithmetical fact knowledge and arithmetic procedures) is a functionally independent component of the calculation system.