A functional magnetic resonance imaging study of mental subtraction in human subjects

The neuronal network involved in a precise type of calculation procedure, m ental subtraction, was investigated by means of functional magnetic resonan ce imaging. Two tasks were used requiring covert production of numbers: (1) with calculation; (2) without calculation. During the first task, activati on was observed in the left dorsolateral prefrontal and premotor cortices, in Broca's area and bilaterally in the inferior parietal cortex. During the second task, activation was mainly observed in Broca's area and to a less extent in the left prefrontal and premotor cortices. Statistical comparison of data in the two situations revealed that the procedure of mental subtra ction is mediated by a distributed system which includes predominantly the left dorsolateral prefrontal cortex and the inferior parietal cortex bilate rally. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.