ABSTRACT
The mechanisms involved in the recognition of operational signs are independent from those involved in accessing “arithmetic facts” and in carrying out calculation procedures. The computational structure of the calculation and number processing system that emerges from neuropsychological analyses has been discussed so far without explicit reference to other cognitive systems. Anatomo-clinical correlates of calculation and number processing have been studied rather unsy stematically. The main results of the cognitive neuropsychological approach to the study of acquired disorders of calculation and number processing have been briefly discussed, along with some hypotheses on the correlations between these processes and brain structures. Cognitive models of calculation and number processing are increasingly more detailed and computationally more explicit. The mechanisms involved in processing numbers for input and for output also serve as input and output mechanisms for the calculation system.
