Neural correlates of mathematical reasoning: An fMRI study of word-problem solving

We examined brain activation, as measured by functional magnetic resonance imaging, during mathematical problem solving in six young, healthy participants. Participants solved problems selected from the Necessary Arithmetic Operations Test (NAOT) which is known to correlate with fluid reasoning tasks. In three conditions, participants solved problems requiring (1) one operation (Easy problems), (2) two operations (Hard problems) or (3) simple reading and matching of words (Match problems) in order to control for perceptual, motor and text reading demands of the NAOT problems. Major bilateral frontal activation and minimal posterior activation was observed while subjects solved Easy problems relative to Match problems. Minor bilateral frontal, temporal and lateralized activation of left parietal regions was observed in the Hard problems relative to Easy problems. All of these regions were activated more by Hard than by Match problems. Many of these activations occurred in regions associated with working memory. These results suggest that fluid reasoning is mediated by a composite of working memory systems that include central executive and domain specific numerical and verbal working memory.