Neural correlates of serial abacus mental calculation in children: a functional MRI study

Abacus experts have demonstrated extraordinary potential of mental calculation by using an imaginary abacus. But the neural correlates of abacus mental calculation and the imaginary abacus still remain unclear. Here, we report, respectively, the analysis of fMRI images of abacus experts and non-experts in response to the performance of simple and complex serial calculation by visual stimuli as well as the images of the abacus experts with performance of the same tasks by auditory stimuli. We found that activated areas were quite different between two groups. In experts, enhanced activations were mainly observed in fronto-temporal circuit (lateral premotor cortex (LPMC) and posterior temporal areas) in simple addition, but in fronto-parietal circuit (lateral premotor cortex (LPMC) and posterior superior parietal lobe (PSPL)) in complex one. By contrast, in controls, the activated areas were almost similar in both simple and complex tasks, including bilateral inferior parietal lobule, prefrontal and premotor cortices. Furthermore, visual and auditory stimuli generated almost similar activations in experts. These observations reveal that (1) abacus mental calculation induces special patterns of brain response, and simple and complex tasks are sustained by dissociated brain circuits between the temporal and parietal cortices, respectively; (2) the abacus mental calculation may rely on neural resources of visuospatial representations with a super-modal form of abacus beads; (3) the posterior temporal areas and PSPL may be recruited for imaginary abacus.