Plural information processing and a large neural network are necessary for numerical processing

Calculation is not a unitary cognitive function. Instead, it is supported by multiple and interrelated neurocognitive components subserved by functional brain networks. In this review, we first address the roles of particular cognitive components in supporting number processing that have been highlighted by previous neuropsychological case reports of isolated acalculia or dissociable calculation deficits. Second, the clinical importance of dissociation of exact/approximate calculation is emphasized. Our patient with global aphasia caused by a large left-hemisphere lesion¹ presented with well-preserved approximate calculation, despite severely impaired exact calculation, thereby indicating that dissociable neurocognitive mechanisms may underlie different calculation abilities. Lastly, based on recent functional neuroimaging studies, we propose that calculation is subserved by a wide range of brain networks, including the left parietal lobe and left frontal lobe, as well as the right cerebral hemisphere.