Neuroanatomical substrates of Arabic number processing, numerical comparison, and simple addition: A PET study

Positron emission tomography was used to localize the cerebral networks spe cifically involved in three basic numerical processes: arabic numeral proce ssing, numerical magnitude comparison, and retrieval of simple addition fac ts. Relative cerebral brood flow changes were measured while normal volunte ers were resting with eyes closed, making physical judgment on nonnumerical characters or arabic digits, comparing, or adding the same digits. Process ing arabic digits bilaterally produced a large nonspecific activation of oc cipito-parietal areas, as well as a specific activation of the right anteri or insula. Comparison and simple addition fact retrieval revealed a fronto- parietal network involving mainly the left intraparietal sulcus, the superi or parietal lobule and the precentral gyrus. Comparison also activated, but to a lesser extent, the right superior parietal lobe, whereas addition als o activated the orbito-frontal areas and the anterior insula in the right h emisphere. Implications for current anatomo-functional models of numerical cognition are drawn.