Coordination Of Bimanual Movements Research Articles

Coordination of Uncoupled Bimanual Movements by Strictly Timed Interhemispheric Connectivity

Independent use of both hands is characteristic of human action in daily life. By nature, however, in-phase bimanual movements, for example clapping, are easier to accomplish than anti-phase movements, for example playing the piano. It is commonly agreed that interhemispheric interactions play a central role in the coordination of bimanual movements. However, the spatial, temporal, and physiological properties of the interhemispheric signals that coordinate different modes of bimanual movements are still not completely understood. More precisely, do individual interhemispheric connectivity parameters have behavioral relevance for bimanual rapid anti-phase coordination? To address this question, we measured movement-related interhemispheric interactions, i.e., inhibition and facilitation, and correlated them with the performance during bimanual coordination. We found that movement-related facilitation from right premotor to left primary motor cortex (rPMd-lM1) predicted performance in anti-phase bimanual movements. It is of note that only fast facilitation during the preparatory period of a movement was associated with success in anti-phase movements. Modulation of right to left primary motor interaction (rM1-lM1) was not related to anti-phase but predicted bimanual in-phase and unimanual behavior. These data suggest that strictly timed modulation of interhemispheric rPMd-lM1 connectivity is essential for independent high-frequency use of both hands. The rM1-lM1 results indicate that adjustment of connectivity between homologous M1 may be important for the regulation of homologous muscle synergies.

Neurophysiologische Diagnostik interhemisphärischer motorischer Bahnen bei neurodegenerativen Erkrankungen

The corpus callosum (CC) is the morphological correlate of inter-hemispheric connectivity. Its integrity is of great importance for motor function and inter-hemispheric coordination of bimanual movements. Callosal fibre tracts show a high vulnerability as they are involved in number of neurodegenerative disease like parkinsonian syndromes and amyotrophic lateral sclerosis, even at early stages of the diseases. The integrity of callosal fibre bundles may be investigated by magnetic resonance imaging techniques and electrophysiologically by transcranial magnetic stimulation (TMS) investigating the transcallosal inhibition (TI). TMS investigation of the TI may be performed by measurement of the ipsilateral silent period (iSP). Most common findings are a loss or a prolongation of the iSP latency. Alternatively, a double pulse paradigm may be used to demonstrate altered TI. Furthermore, the transcallosal conduction time may be lengthened. TMS investigation of TI may a helpful diagnostic tool and may give new insights into the pathophysiology.

Re-examining structural constraints on the initiation of bimanual movements: The role of starting locations, movement amplitudes, and target locations

Structural constraints affect the coordination of bimanual movements in ways that have been taken to suggest that the specification of different movement amplitudes is subject to strong intermanual interference effects. Most experiments taken to support this notion, however, confounded variations of movement amplitudes with symmetry in starting locations and variations in target location. The present experiment was designed to further investigate the relative influence of the parameters starting location, movement amplitude, and target location on bimanual movement coordination. Participants performed simultaneous reaching movements with the left and right hand from same and different starting locations to same and different target locations. On each trial, two movements could match on none, one, or all of the parameters. We assessed the influence of each parameter by comparing conditions in which only a single parameter matched between the two hands with conditions in which all parameters differed. The reaction-time data revealed some challenging results for previous studies: (1) same starting locations significantly delayed movement initiation; (2) specifying movement amplitudes had virtually no effect on movement initiation, whereas (3) selecting same target locations significantly benefited the bimanual responses. These findings cannot be taken to support the notion that amplitude specification affects the initiation of bimanual movements. Rather, they support the notion that the initial starting locations of the two hands and the selection of target locations decide about the ease with which we perform bimanual reaching movements.