Neuroimaging evidence points towards the left inferior parietal cortex to be crucial for the representation and retrieval of multiplication facts. However, to date studies allowing a functional interpretation of neuroimaging data are still scarce. In the current study we aimed at evaluating the functional involvement of left inferior parietal cortex areas in the implicit retrieval of multiplication fact knowledge in a number bisection task by examining event-related desynchronization (ERD) in the upper alpha band. Upper alpha ERD is generally agreed to be modulated by processes of memory retrieval. It was observed that upper alpha ERD decreased for multiplicative triplets (e.g. 3_6_9) but not for non-multiplicative (e.g. 2_5_8) triplets at left parietal electrodes but increased at left prefrontal electrodes. These results are interpreted to suggest that after multiplicativity has been recognized further magnitude evaluations in the left hemisphere may be abated by prefrontal processes of executive control.
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