Algebra in a man with severe aphasia.

We report a dissociation between higher order mathematical ability and language in the case of a man (SO) with severe aphasia. Despite severely impaired abilities in the language domain and difficulties with processing both phonological and orthographic number words, he was able to judge the equivalence of and to transform and simplify mathematical expressions in algebraic notation. SO was sensitive to structure-dependent properties of algebraic expressions and displayed considerable capacity to retrieve algebraic facts, rules and principles, and to apply them to novel problems. He demonstrated similar capacity in solving expressions containing either solely numeric or abstract algebraic symbols (e.g., 8-(3-5)+3 versus b-(a-c)+a). The results show the retention of elementary algebra despite severe aphasia and provide evidence for the preservation of symbolic capacity in one modality and hence against the notion of aphasia as asymbolia.