Numerical abilities in dementia

Abstract

The purpose of the present paper is to provide a critical review of the neuropsychological evidence elucidating the incidence and nature of numerical difficulties in dementia. Though long neglected, the occurrence of dyscalculia in the early stage of Alzheimer's disease (AD) has caught the attention of many, and both group studies and single-case investigations converge in identifying number processing and numerical difficulties among the early signs of dementia. Yet analysis of the available data suggests that the pattern of decline may vary greatly across individuals: numerical difficulties may be highly selective and limited to single processing mechanisms but also extended to all aspects of numerical abilities. Overall, data from AD, in agreement with acquired disorders in focal lesioned patients, confirm the dissociations between multiple functional components of the number processing and calculation system.