Cortical activation during retrieval of arithmetical facts and actual calculation: A functional magnetic resonance imaging study

By using functional magnetic resonance imaging (fMRI), the neural substrate s involved in mental recitation of the single-digit multiplication table an d serial subtraction were studied. The former depends mostly on well-learne d arithmetical facts, while the latter requires arithmetic processing. Acti vation during each task was compared with that in a number counting control . During the recitation of single-digit multiplication, the activated regio ns included the area lying along the left intraparietal sulcus, the premoto r and supplementary motor areas, and the posterior portion of the left infe rior frontal gyrus. The areas activated during serial subtraction included these areas as well as the bilateral prefrontal and right parietal areas. F rom the results obtained during retrieval of the multiplication table in th is study and previous studies, it was concluded that semantic memory of the multiplication table is stored in the area lying along the intraparietal s ulcus and that the frontal areas play an executive role in utilizing the se mantic memory of arithmetical facts. It was assumed that the arithmetical f acts requiring actual calculation are also stored in the same region. The a dditional activation during serial subtraction compared with the activation during retrieval of the multiplication table is probably due to the proces ses of actual calculation. These processes include proper alignment of digi ts, which may have caused the right parietal activation, and maintaining di gits needed for the mental serial subtractions, which may have caused the b ilateral prefrontal activation.