Cerebral activation during multiplication: a functional MR imaging study of number processing.

BACKGROUND AND PURPOSE Current models of brain function propose that number processing involves the interaction of different neuronal networks. Our purpose was to use functional MR (fMR) imaging to elucidate the brain regions engaged by multiplication. METHODS Eighteen adults underwent fMR imaging while performing matching, multiplication, and control tasks. For each task, three or four single-digit or low-value double-digit numbers were presented serially followed by a 12-second delay. A target stimulus then appeared and subjects made a judgement by pressing a button box that recorded responses. During the matching task, subjects judged whether the target stimulus matched one of the previous numbers. During the multiplication task, subjects judged whether the target stimulus was the product of the previous numbers. For the control task, the numbers were always zeros, and the subjects responded to a target stimulus that was always four zeros. Composite statistical parametric maps of the time course of activation comparing the control task with the matching and multiplication tasks, respectively, were generated and the significance of signal changes was estimated by randomization of statistical parametric maps. RESULTS The matching and multiplication tasks resulted in activation (P < .005) in the medial superior frontal gyrus; the anterior cingulate gyrus; the intraparietal sulci, bilaterally; the right superior frontal sulcus bilaterally; the middle, inferior and precentral frontal gyri (left greater than right); the left basal ganglia; and the right lateral and inferior occipital gyri. There was a larger area of early activation in the right middle frontal gyrus during the matching task compared with the multiplication task, and there was a longer interval of activation in the left middle frontal gyrus during the multiplication task (10 seconds) than in the matching task (6 seconds). CONCLUSION Multiplication and memory of numbers share an integrated network of brain regions. The left frontal lobe, an area also involved in memory and language processes, appears to play an important role in multiplication.