fMRI study of bimanual coordination

Eleven right-handed subjects performed uni- and bimanual tapping tasks. Hem odynamic responses as measured with functional magnetic resonance imaging ( fMRI) in the primary somato-motor cortex (SMC) showed that during bimanual activity the SMC contralateral to the hand taking the faster rate was more strongly activated than the SMC contralateral to hand taking the slower rat e. There were no asymmetries; left SMC activation during the right fast/lef t slow tapping condition was comparable to the right SMC activation during the left fast/right slow condition. A given SMC showed similar activation l evels for bimanual and unimanual activity (i.e. left SMC activation for rig ht fast/left slow was similar to left SMC activation for the right fast uni manual condition). In contrast, a given supplementary motor area (SMA) show ed significantly more activation for the bimanual than for the unimanual ac tivity. In addition, an asymmetry was observed during bimanual activities: during the right fast/left slow activity, the left SMA showed more activati on than the right SMA, but during the left fast/right slow activity, the ri ght SMA was not significantly more activated than the left SMA. For unimanu al activities, a clear rare effect (greater activation for faster rate) was seen in the SMC but not in the SMA. (C) 1999 Elsevier Science Ltd. All rig hts reserved.