Research reportDissociated brain organization for two-digit addition and subtraction: An fMRI investigation

The present study compared the patterns of brain activation elicited by two-digit addition and subtraction problems. Thirty-two Chinese undergraduates of the same educational background and of similar age were asked to assess whether arithmetic operations were true or false during functional magnetic resonance imaging. Results showed that both complex addition and subtraction were supported by the broad neural system that involved regions within the inferior parietal lobule, the precuneus, and the inferior occipital gyrus, as well as some subcortical structures. Nevertheless, complex problems involving addition elicited more activation mainly in the bilateral medial frontal gyrus, whereas problems involving subtraction had more activation in the precentral gyrus and the thalamus in the right hemisphere, as well as the inferior parietal lobule in the left hemisphere. This pattern of dissociated activation suggests that partially separate neuronal networks might support these different operations. It also suggests that complex addition has a greater reliance on the fronto-parietal cortical circuit and subtraction on the parieto-subcortical circuit.

► A mixture of additions and subtractions is widely used in variety of mathematical cognitive tests, but our study focused on separating additions and subtractions to emphasize the differences. ► Experimental design of our study has splitted levels of difficulty in calculation. ► Brain-imaging data revealed that the pulvinar and the thalamocortical projection regions were activated in participants under the subtraction conditions. ► Behavioral data showed that participants have low degrees of accuracy and longer response time in subtraction task.