Jayasinghe S A L
Division of Physical Therapy and Rehabilitation Science, Department of Family Medicine and Community Health, University of Minnesota, Minneapolis, Minnesota, United States.
J Neurophysiol. 2025 Jan 1;133(1):60-68. doi: 10.1152/jn.00167.2024. Epub 2024 Dec 3.
Although the dominant hand has been shown to have performance advantages over the nondominant hand, these interlimb differences have found to be dependent on task and biomechanical demands. The dynamic dominance hypothesis suggests that the left hemisphere is specialized for the control of intersegmental dynamics while the nondominant right hemisphere is specialized for postural control, in right-handers. In a real-world scenario, however, cognitive challenges might be expected to modulate these specialized behaviors. Therefore, we hypothesized that with increased cognitive load, lateralized motor control processes would become even more asymmetrical. We recruited 16 right-handed older adults (11 females, 5 males; 65.88 yr ± 1.99 SE) to perform 170 trials of a unilateral reaching task with each of their hands on the Kinereach system. In each trial, participants rapidly memorized pictorial instructions before identifying and reaching for the correct object on a screen. The complexity of the task increased over the course of the experiment. Our results demonstrated higher reaction times in the right than in the left hand ( = 0.0004). Movements became increasingly curved and erroneous with cognitive load, but interlimb differences in movement quality were absent. We found higher joint cocontraction in the right than in the left arm ( < 0.05), but these differences were unaffected by cognitive load. Hence, with the addition of a cognitive load, we observed asymmetries in reaction time but not in joint coordination or movement quality. This highlights the role of cognitive load in modulating limb/hemisphere specializations for control processes. Although we know that motor control processes are lateralized to each hemisphere, the role of cognitive load on these specialized processes is undefined. We designed a unique task that incorporates a cognitive challenge to a typical reaching movement to examine how cognitive load affects limb asymmetries in motor control. In a group of typical older adults, we demonstrated interlimb asymmetries in reaction time but not in joint coordination or movement quality.
尽管已表明优势手在表现上优于非优势手，但这些肢体间的差异取决于任务和生物力学需求。动态优势假说认为，在右利手中，左半球专门负责节段间动态的控制，而非优势的右半球专门负责姿势控制。然而，在现实场景中，认知挑战可能会调节这些专门的行为。因此，我们假设随着认知负荷的增加，偏侧化的运动控制过程会变得更加不对称。我们招募了16名右利手的老年人（11名女性，5名男性；年龄65.88岁±1.99标准误），让他们用双手在Kinereach系统上各进行170次单侧伸手任务试验。在每次试验中，参与者在识别并伸手去够屏幕上正确的物体之前，要快速记住图片指令。在实验过程中，任务的复杂性不断增加。我们的结果显示，右手的反应时间比左手长（ = 0.0004）。随着认知负荷的增加，动作变得越来越弯曲且错误，但动作质量的肢体间差异并不存在。我们发现右臂的关节共同收缩比左臂更高（ < 0.05），但这些差异不受认知负荷的影响。因此，随着认知负荷的增加，我们观察到反应时间存在不对称，但关节协调性或动作质量不存在不对称。这突出了认知负荷在调节控制过程中肢体/半球专门化方面的作用。尽管我们知道运动控制过程在每个半球是偏侧化的，但认知负荷对这些专门过程的作用尚不清楚。我们设计了一项独特的任务，将认知挑战融入到典型的伸手动作中，以研究认知负荷如何影响运动控制中的肢体不对称。在一组典型的老年人中，我们证明了反应时间存在肢体间不对称，但关节协调性或动作质量不存在不对称。
