Influence of cognitive strategies on the pattern of cortical activation during mental subtraction. A functional imaging study in human subjects

Functional magnetic resonance imaging (fMRI) at 1.5 T was used to investiga te the influence of cognitive strategies on cortical activation during ment al calculation. Twenty-nine right-handed subjects performed a serial subtra ction of prime numbers. Even though a common corpus of brain areas was acti vated during this mental calculation, differences appeared between subjects in function of their spontaneous cognitive strategy. In subjects using a s o called verbal strategy (n = 15), the main activation was located in the w hole left dorsolateral frontal cortex with a little activation of the infer ior parietal cortex. In subjects using a so called visual strategy (n = 14) , a bilateral activation in the prefrontal cortex and a high activation in the left inferior parietal cortex were observed. These results demonstrate that numbers are processed through a distributed network of cortical areas, the lateralization of which is clearly influenced by subject strategy. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.