How the brain handles temporally uncoupled bimanual movements.

Whereas the cerebral representation of bimanual spatial coordination has been subject to prior research, the networks mediating bimanual temporal coordination are still unclear. The present study used functional imaging to investigate cerebral networks mediating temporally uncoupled bimanual finger movements. Three bimanual tasks were designed for the execution of movements with different timing and amplitude, with same timing but different amplitude, and with same timing and amplitude. Functional magnetic resonance imaging results showed an increase of activation within right premotor and dorsolateral prefrontal, bilateral inferior parietal, basal ganglia, and cerebellum areas related to temporally uncoupled bilateral finger movements. Further analyses showed a decrease of connectivity between homologous primary hand motor regions. In contrast, there was an increase of connectivity between motor regions and anterior cingulate, premotor and posterior parietal regions during bimanual movements that were spatially or both temporally and spatially uncoupled, compared with bimanual movements that were both spatially and temporally coupled. These results demonstrate that the extent of bihemispheric coupling of M1 areas is related to the degree of temporal synchronization of bimanual finger movements. Furthermore, inferior parietal and premotor regions play a key role for the implementation not only of spatial but also of temporal movement parameters in bimanual coordination.