Auditory task presentation reveals predominantly right hemispheric fMRI activation patterns during mental calculation

Neuroimaging and lesion studies suggest that a network of different brain areas are involved in mental calculation processes. Indeed, little is known about the comparability of brain activation across studies because of the variety of different design parameters. The experiment reported in the present study examined response times and fMRI-BOLD activity patterns in normal volunteers for calculation tasks entailing addition, subtraction, multiplication and division tasks of different complexities from auditory stimulation. FMRI data showed activation patterns in bilateral superior frontal, adjacent to medial frontal regions, and in right precuneus as revealed by conjunction analysis. All other regional activations appeared to be operation-specific and distributed in predominantly right hemispheric frontal, parietal and central regions. It is concluded that both operation and task presentation modalities can have significant influence on the mobilization of regional neuronal networks required for mental calculation processes. Therefore, it is suggested that results from different studies should only be compared directly when analogous presentation modalities and operators were used in the applied experimental designs.