Interlimb Differences in Multi-degree-of-freedom Coordination During Cyclic Bilateral and Unilateral Wrist Movements

Download or read book Interlimb Differences in Multi-degree-of-freedom Coordination During Cyclic Bilateral and Unilateral Wrist Movements written by Kristen Selby and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The dynamic dominance hypothesis of motor lateralization proposes that in right-handed individuals, the left hemisphere is specialized for intersegmental limb coordination and predictive control, and the right hemisphere is specialized for impedance control. This model predicts a dominant arm advantage for intersegmental coordination which has largely been demonstrated in discrete reaching movements. However, much of this work is restricted to unilateral conditions and many of the tasks we perform in everyday life require use of both limbs simultaneously. We now ask whether this coordination advantage extends to bilateral movements. Our dynamic dominance hypothesis predicts that interlimb differences in coordination should persist for single segment, multiarticular cyclic movements and that they should persist during bimanual movements. Research on bimanual coordination seems to be split between literature suggesting a 'coupling' under bimanual movements, with limbs favoring synchronous and symmetric movements, while other lines of work focus on asynchronies and asymmetries between the dominant and non-dominant during bimanual movements, including a dominant arm advantage. This has led to competing hypotheses for bimanual coordination, with interlimb 'coupling' hypotheses predicting that limbs become more symmetric and synchronous during bimanual movements due to a preference for functional muscle groups to act as a single unit, allowing central control mechanisms to utilize one control signal for both limbs. An alternative view of bimanual coordination can be referred to as a goal-equivalent hypothesis, which predicts that interlimb differences are only constrained when they are detrimental to task performance. To investigate these hypotheses of bimanual coordination, we created a task with multiple degrees of freedom in which redundant movements were not restrained. Thirty-two right-handed young adults performed cyclic horizontal plane wrist movements, largely reflected by radial-ulnar deviation. Movements were performed both unilaterally and bilaterally at two frequencies. Participants were instructed to restrict movements to the horizontal plane. Movements outside of the task plane were measured and quantified as vertical displacement and coordination of the multiple degrees of wrist movement was quantified as wrist circumduction. Regardless of instructed frequency, the non-dominant hand displayed significantly greater circumduction. Interestingly, in bilateral movements, circumduction was greater than unilateral movements for both hands, however interlimb differences persisted. This asymmetry supports the predictions of the dynamic dominance hypothesis and extends the hypothesis to multi-degree-of-freedom distal segments. Our findings also align with a goal-equivalent hypothesis, as out-of-task plane coordination was not symmetric during bimanual conditions, suggesting that tendencies for motor symmetry only apply to movements contributing to the task goal.