Regional cerebral differences in activation by two types of calculation, quantitative number processing and use of rote verbal arithmetic memory, were investigated.
Methods: The two types of processing were induced by serial number subtraction (the Subtra-task) and recitation of the multiplication table (the Multi-task), respectively. Regional cerebral blood flow (rCBF) under the two tasks was measured in ten healthy right-handed Japanese men using (15)O-labeled water and positron emission tomography (PET). Statistical parametric mapping (SPM) was used for estimating rCBF differences during these tasks.
Results: The activated areas during the Subtra-task were consistent with those reported to be involved in quantitative number processing. Although most of the regions activated during the Multi-task were in common with the regions activated during the Subtra-task, the spatial extent of the activation during the Multi-task was smaller. Moreover, the left lenticular nucleus was activated during the Multi-task, but not in the Subtra-task, while the prefrontal cortex was activated in the Subtra-task but not in the Multi-task.
Conclusion: The difference in the regions activated by the two tasks, and the difference in the spatial extent of each region by the two tasks indicated that the anatomical networks of the two processes were segregated.