A case of severe acalculia derived from a right hemisphere lesion

The present paper describes a case of severe acalculia derived from right-hemisphere lesion. The patient (LLS) did not merely present the symptoms expected after a right hemisphere lesion, such as a generic inability to deal with spatial material, or from other deficits, such as neglect; the patient was also unable to complete simple addition and multiplication but with preserved general verbal ability. The implications of these symptoms are discussed in the context of the noted theoretical models that have been proposed for the cognitive mechanisms underlying number processing and calculation skills.