Cerebral Cortex Advance Access originally published online on January 4, 2006
Cerebral Cortex 2006 16(12):1729-1738; doi:10.1093/cercor/bhj108
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Goal-Selection and Movement-Related Conflict during Bimanual Reaching Movements
1 Department of Biomedical Engineering, Johns Hopkins University, 720 Rutland Avenue, 419 Traylor Building, Baltimore, MD 21205, USA, 2 Department of Psychological and Brain Sciences, Dartmouth College, 6207 Moore Hall, Hanover, NH 03755, USA, 3 Department of Psychology, University of California, Berkeley, Tolman Hall #1650, CA 94720, USA, 4 Department of Psychology, University of Iowa, 11 Seashore hall E, Iowa City, IA 52242, USA
Address correspondence to Jörn Diedrichsen, Department of Biomedical Engineering, Johns Hopkins University, 720 Rutland Avenue, 419 Traylor Building, Baltimore, MD 21205, USA. Email: jdiedric{at}jhu.edu.
Conflict during bimanual movements can arise during the selection of movement goals or during movement planning and execution. We demonstrate a behavioral and neural dissociation of these 2 types of conflict. During functional magnetic resonance imaging scanning, participants performed bimanual reaching movements with symmetric (congruent) or orthogonal (incongruent) trajectories. The required movements were indicated either spatially, by illuminating the targets, or symbolically, using centrally presented letters. The processing of symbolic cues led to increased activation in a left hemisphere network including the intraparietal sulcus, premotor cortex, and inferior frontal gyrus. Reaction time cost for incongruent movements was substantially larger for symbolic than for spatial cues, indicating that the cost was primarily associated with the selection and assignment of movement goals, demands that are minimized when goals are directly specified by spatial cues. This goal-selection conflict increased activity in the pre–supplementary motor area and cingulate motor areas. Both cueing conditions led to larger activation for incongruent movements in the convexity of the superior parietal cortex, bilaterally, making this region a likely neural site for conflict that arises during the planning and execution of bimanual movements. These results suggest distinct neural loci for 2 forms of constraint on our ability to perform bimanual reaching movements.
Key Words: bimanual • fMRI • human • parietal lobe • reaching
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