[Quantitative numerical and lexical knowledge: evidence of double dissociation].

The aim of this work was to explain the involvement of a specific brain injury in the numerical processing and calculation system. The method employed was > analysis and the administration of various cognitive neuropsychology tests. The results of this study revealed a double dissociation between quantitative numerical knowledge and qualitative or lexical numerical knowledge. Patient M.C. preserved quantitative numerical knowledge, as indicated by the results obtained in the numerical comprehension and calculation tasks. However, she showed a drastic deficit in qualitative numerical knowledge. On the other hand, patient M.L. preserved qualitative numerical knowledge, but she had serious problems in all the abilities that require internal manipulation of magnitude; that is, quantitative numerical knowledge. These results have two important implications, as conclusions: firstly, quantitative numerical knowledge may be made up of different elements susceptible to damage independently. And secondly, quantitative and qualitative numerical knowledge were functionally independent.