ABSTRACT
J. Grafman, D. Passafiume, P. Faglioni, and F. Boller endeavored to evaluate the role played by visuo-spatial disorders in subjects with impaired calculation abilities. Although in good agreement with the generally accepted preponderance of acalculia after parieto-occipital lesions, which are known to produce visuospatial disorders. Most of the earlier authors held that it is the parieto-occipital region of the language-dominant hemisphere that is critically involved in arithmetical abilities. Indirect evidence with regard to the importance of left and right hemispheric lesions can be derived from the experimental studies of Grafman et al. and W. Dahmen et al. Both studies agree that posterior lesions of either hemisphere are found to lead to greater impairment of arithmetical performance than anterior lesions, and that the severest impairment is observed with left posterior lesions. The partial support for an intrinsic link between spatial and arithmetical activities provided by the results of Dahmen et al.
