Nigrostriatal dopamine system and motor lateralization

The mechanism by which most people favor use of the right hand remains unkn own. It has been proposed that asymmetries in the nigrostriatal dopamine sy stem may be related to motor lateralization in humans. We explored this hyp othesis in vivo by using [F-18]fluorodopa positron emission tomography. Whe reas the degree of right hand preference was found to correlate with left p utamen dominance as assessed by asymmetry in fluorodopa uptake (K-i), right caudate dominance was positively correlated with the level of performance during simultaneous bimanual movements in right-handed normal subjects. In addition, right-handed patients with Parkinson's disease with higher right than left caudate K-i performed much better in bimanual movement tests than those in whom the K-i value of the left caudate was higher than that of th e right. These findings support the notion that the nigrostriatal dopaminer gic system may play a role in motor lateralization, and suggest a functiona l model for bimanual movements. We propose that the skill for performing si multaneous bilateral hand movements in right-handed subjects might depend u pon both the activation (through the dominant left putamen circuitry) of th e left supplementary motor area (SMA), and the inhibition (through the righ t caudate circuitry) of motor programs stored in the right SMA. (C) 2000 El sevier Science B.V. All rights reserved.