Abstract
The present study aimed at exploring basic number and calculation abilities in right-hemisphere damaged patients (RHD), focusing primarily on one-digit orally presented tasks, which do not require explicit visuo-spatial abilities. Twenty-four non mentally-deteriorated RHD patients [12 with clinical neglect (RHDN+), 12 without clinical neglect (RHDN−)], and 12 healthy controls were included in the study. Participants were administered an ad hoc numerical battery assessing abilities such as counting, number magnitude comparison, writing and reading Arabic numerals and mental calculation, among others. Significant differences emerged among healthy controls and both the RHDN+ group and the RHDN− group, suggesting that the mathematical impairment of RHD patients does not necessarily correspond to the presence of left-neglect. A detailed analysis of the sub-tests of the battery evidenced expected differences among RHDN+ patients, RHDN− patients, and controls in writing and reading Arabic numerals. Crucially, differences between RHDN+ patients and controls were also found in tasks such as mental subtraction and mental multiplication, which do not require written visuo-spatial abilities. The present findings thus suggest that unilateral right hemisphere lesions may produce specific representational deficits that affect simple mental calculation, and not only the spatial arrangement of multi-digit written numbers as previously thought.
Highlights
The first to point out a possible contribution of the right hemisphere to calculation was Henschen (1926)
Similar results were obtained after excluding reading and writing numbers to dictation from the Numerical Screening, which were the only two tasks requiring explicit visuo-spatial abilities in the battery. After excluding these tasks there was a significant effect of Group [χ(22,N=36) = 16.95; p < 0.0005], due to differences between the RHDN+ group and healthy controls (p < 0.0005), between the RHDN− group and healthy controls (p < 0.01), and between RHDN+ and RHDN− groups (p < 0.005)
Our study examined whether basic calculation and number processing would be affected by the presence of left neglect (LN) after righthemisphere damage
Summary
The first to point out a possible contribution of the right hemisphere to calculation was Henschen (1926). Sperry et al (1969) argued from the study of split-brain patients that the capacity for calculation of the right hemisphere is “almost negligible.”. To this day, acalculia following a right hemisphere lesion is a very poorly defined entity. Acalculia following a right hemisphere lesion is a very poorly defined entity It is consistently found in groupstudies, though in various proportions partly due to the different sensitivity of the calculation tests used to assess patients. Most studies appear incomplete because they excluded neglect patients, and some considered only retrorolandic patients
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