Bimanual finger synergies reveal no functional asymmetry between hands

The complex movements of the dominant (DOT) and non-dominant (NDOT) hands during bimanual tasks can be represented using a smaller number of control units, known as bimanual synergies. A weighted combination of these synergies could be used to construct a large array of bimanual movements. Neuroscience research, particularly through the dynamic dominance hypothesis (DDH), has suggested a distinct control scheme for the proximal DOT and NDOT hands. However, studies demonstrating such differences for the distal segment are scarce, and the results are mixed. This study compares the bimanual kinematic synergies of the DOT and NDOT hands during bimanual manipulation tasks. Sixteen right-handed participants performed eight tasks in two sessions using an inertial measurement unit (IMU)-based system. In the first session, the participants used their DOT hand to manipulate objects while the NDOT was used to hold the object steady. In the second session, the roles of the hands were reversed to increase task demands. Comparison of the bimanual synergies obtained during the two sessions showed a high similarity in synergies between the DOT and NDOT hands. Analysis of reconstruction errors further confirmed these results, demonstrating minimal differences between the two hands. This indicates that the central nervous system (CNS) uses a coordinated approach for both hands, relying on interhemispheric communication and coordination between cortical and subcortical structures. The CNS demonstrates a high degree of adaptability, ensuring similar patterns between hands even under increased task demands. These findings could have significant implications for rehabilitation, providing valuable insights into motor control mechanisms.