Division of Physical and Health Education, Graduate School of Education, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan, Japan Society for the Promotion of Science, Chiyoda-ku, Tokyo 102-8471, Japan, and Institute of Cognitive Neuroscience, University College London, London WC1N 3AR, United Kingdom
Division of Physical and Health Education, Graduate School of Education, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
J Neurosci. 2014 Jul 2;34(27):9141-51. doi: 10.1523/JNEUROSCI.2694-13.2014.
It is generally believed that the dominant arm exhibits greater functional advantages over the nondominant arm in every respect, including muscular strength and movement accuracy. Recent studies have proposed that this laterality is due to different underlying control strategies for each limb rather than different limb capabilities constraining performance. However, the functional role and mechanisms of these different control strategies have yet to be elucidated. Here, we report a specialized function of the nondominant arm that plays a significant role only during bimanual movements. Right-handed human participants performed bimanual reaching movements while only one arm was subjected to a force field. Consistent with our previous study, adaptation to the force field decreased gradually as the movement direction of the opposite arm deviated from the trained direction. We also observed that the decrement of the adaptation was significantly greater for the nondominant left arm. According to our previously proposed theory, this poorer generalization of the left arm originated from a difference in parameters characterizing motor memory; the nondominant arm's motor memory was more strongly influenced by the opposite arm's kinematics. Remarkably, a model incorporating this lateralized memory predicted that the nondominant arm would demonstrate greater adaptability to force fields associated with the opposite arm's movement. We confirmed this prediction experimentally and found that this advantage of the left arm disappeared in left-handed human participants. We concluded that the secondary supporting role often played by the nondominant arm in bimanual actions reflects its specialization rather than its inferiority.
人们普遍认为，无论在肌肉力量还是运动精度方面，优势臂在各方面都优于非优势臂。最近的研究提出，这种偏侧性是由于每条肢体的控制策略不同，而不是肢体能力的不同限制了运动表现。然而，这些不同控制策略的功能作用和机制仍有待阐明。在这里，我们报告了非优势臂的一种特殊功能，这种功能仅在双手运动中发挥重要作用。右利手的人类参与者在只有一只手臂受到力场作用的情况下进行双手臂的伸展运动。与我们之前的研究一致，当另一只手臂的运动方向偏离训练方向时，对力场的适应逐渐减弱。我们还观察到，非优势的左臂的适应程度下降更为明显。根据我们之前提出的理论，这种左臂较差的泛化源于表征运动记忆的参数的差异；非优势臂的运动记忆受对侧手臂运动学的影响更大。值得注意的是，纳入这种偏侧化记忆的模型预测，非优势臂将表现出更大的适应与对侧手臂运动相关的力场的能力。我们通过实验证实了这一预测，并发现这种左手参与者的左优势臂的优势消失了。我们得出结论，非优势臂在双手动作中经常扮演次要的辅助角色，这反映了它的专业化，而不是它的劣势。
