CEREBRAL ACTIVATIONS DURING NUMBER MULTIPLICATION AND COMPARISON - A PET STUDY

Positron emission tomography was used to examine the cerebral networks underlying number comparison and multiplication in eight normal volun teers. Cerebral blood flow was measured within anatomical regions of i nterest defined in each subject using magnetic resonance imaging. Thre e conditions were used: rest with eyes closed, mental multiplication o f pairs of arabic digits and larger-smaller comparison of the same pai rs. Both multiplication and comparison activated the left and right la teral occipital cortices, the left precentral gyrus, and the supplemen tary motor area. Beyond these common activations, multiplication activ ated also the left and right inferior parietal gyri, the left fusiform and lingual gyri, and the right cuneus. Relative to comparison, multi plication also yielded superior activity in the left lenticular nucleu s and in Brodmann's area 8, and induced a hemispheric asymmetry in the activation of the precentral and inferior frontal gyri. Conversely, r elative to multiplication, comparison yielded superior activity in the right superior temporal gyrus, the left and right middle temporal gyr i, the right superior frontal gyrus, and the right inferior frontal gy rus. These results underline the role of bilateral inferior parietal r egions in number processing and suggest that multiplication and compar ison may rest on partially distinct networks. Copyright (C) 1996 Elsev ier Science Ltd.