Dissociation of Exact and Approximate Calculation in Severe Global Aphasia
Masayo Urano1, Mariko Yoshino2, Masahiro Yamamoto3, Masaru Mimura*, 4
Identifiers and Pagination:Year: 2009
First Page: 8
Last Page: 12
Publisher Id: TONEUJ-3-8
Article History:Received Date: 24/9/2008
Revision Received Date: 31/10/2008
Acceptance Date: 2/1/2009
Electronic publication date: 30/1/2009
Collection year: 2009
open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.
We report a 68-year-old patient with severe global aphasia secondary to a large left hemisphere infarction including the parietal lobe. In addition to language and neuroradiological evaluation, the patient was given specifically designed arithmetic and clock tasks requiring either exact calculation or approximate calculation. Despite severe language impairment, the patient showed relatively well-preserved abilities for numerical comprehension and arithmetic operations. Further analyses using specifically designed arithmetic and clock tasks demonstrated a clear dissociation of the patient’s abilities between impaired exact calculation and well-preserved approximate calculation. The results support the notion that numerical and arithmetic abilities are heterogeneous in that rote verbal arithmetic facts and quantitative numerical knowledge can be separable. Implications of the present findings for neural correlates of numerical and arithmetic processing suggest that the right hemisphere plays a crucial role in approximate calculation.