Cognitive neuropsychological models of adult calculation and number processing: the role of the surface format of numbers.

Several brain-damaged patients showed a series of performance dissociations related to the surface format of numbers. These findings provide empirical evidence against two crucial assumptions of the calculation and number processing model proposed by McCloskey, Caramazza and Basili (36) and widely accepted within the current literature on developmental dyscalculia. First, the unique syntactical system for verbal numbers can fractionate into two syntactic components, one for spoken verbal and one for written verbal numbers, respectively. Second, access to simple number facts (multiplication tables) seems to rely on format-specific routes and not on the access to supposedly unique abstract representations. The data can also hardly be interpreted within the theoretical framework of the "triple-code" information processing model of Dehaene (16) and of its anatomical implementation by Dehaene and Cohen (19). Taken together, these results favour a cognitive architecture of the numerical system with a variety of format-specific processes and multiple representations proposed by Campbell and Clark (8) which remain to be fully specified.