The Residual Calculation Abilities of a Patient with Severe Aphasia: Evidence for a Selective Deficit of Subtraction Procedures

We report the case study of a severe fluent aphasic patient, who showed relatively preserved numerical abilities. A detailed investigation of number processing indicated good numerical comprehension and a relative sparing of addition and subtraction abilities; on the other hand, multiplication and division were severely impaired. A further study of multi-digit operations showed that the patientʹs performance was characterized by a selective impairment of the borrowing procedure, in which she applied the so-called Smaller-from-Larger bug, typically observed in children learning to calculate. The present case provides further evidence for the dissociation between operations based on verbal sequences and on quantity manipulation, respectively impaired and preserved in patients with severe aphasia. Moreover, it provides evidence indicating that procedures may be dissociated from conceptual knowledge within a single arithmetical operation.