Transcoding and calculation in aphasia

Aphasia may have deteriorating effects on several numerical skills, such as counting, reading numerals aloud, or writing them to dictation, as these abilities rely on intact language. However, aphasia also seems to have specific effects on the calculation system. Group studies, as well as single-case studies, point to the fact that language-impaired patients have particular difficulties in completing multiplication tasks, while other operations are less impaired. From a theoretical point of view, there is still a debate as to whether this association reflects a general psycholinguistic problem, the effect of aphasia on numerical cognition, or a deficit in non-specific resources underlying both number and language domains. In studies on number transcoding multi-route models have been proposed which parallel semantic and asemantic routes in alphabetical processing. Yet, the review of the empirical evidence suggests that these models still lack relevant theoretical specification.