Mặc dù thông tin và dữ liệu lập bản đồ tổn thương não để xử lý số hạn chế, thông tin sẵn có cho thấy các nếp cuộn fusiform và khu vực lân cận song phương trực quan kết hợp vỏ não liên kết chặt chẽ với sự hỗ trợ của các ký hiệu số và truy cập từ vựng số. | Darren R. Gitelman 138 produced a large number of activations fortyseven overlying frontal precentral and prefrontal parietal occipital fusiform and cingulate cortices and the thalamus. Notational effects were seen in the right fusiform gyrus greater activation for Arabic numerals than spelled-out numbers and the left superior precentral gyrus slight prolongation of the hemodynamic response for spelled-out numbers than for Arabic numerals Pinel et al. 1999 . Although lesion information and brain mapping data for numerical processing are limited the available information suggests that the fusiform gyrus and nearby regions of bilateral visual association cortex are closely associated with support of numerical notation and numerical lexical access. It is also tempting to speculate that the syntactic aspects of number processing are served by left posterior frontal regions perhaps in the superior precentral gyrus by analogy with syntactic processing areas for language but this has not been shown conclusively. Calculation Operations Aside from mechanisms for processing numbers a separate set of functions has been posited for performing arithmetical operations. Deficits in this area were formerly described as anarithmetia or primary acalculia Boller Grafman 1985 . The major neuropsychological abnormalities of this subsystem have been hypothesized to consist of deficits in 1 processing operational symbols or words 2 retrieving memorized mathematical facts 3 performing simple rule-based operations and 4 executing multistep calculation procedures McCloskey et al. 1985 . Patients showing dissociated abilities for each of these operations have provided support for this organizational scheme. Numerical Symbol Processing Grewel was one of the first authors to codify deficits in comprehending the operational symbols of calculation. A disorder that he called asymbolia which had been documented in patients as early as 1908 was characterized by difficulty recognizing operational .
