Reduction of Metabolic Cost during Motor Learning of Arm Reaching Dynamics
Reduction of Metabolic Cost during Motor Learning of Arm Reaching Dynamics
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DOI：
10.1523/jneurosci.4003-11.2012
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发表时间：
2012-02-08
影响因子：
5.3
通讯作者：
Ahmed, Alaa A.
中科院分区：
文献类型：
--
作者：
Huang, Helen J.;Kram, Rodger;Ahmed, Alaa A.
人们通常认为中枢神经系统以最小化能量消耗的方式控制运动。虽然运动中存在实际代谢最小化的经验证据，但在运动学习和/或手臂伸展期间尚未测量实际代谢成本。在这里，我们使用呼出气体分析来测量代谢功耗，因为人类学习了新的手臂伸展动力学。我们假设（1）代谢能力会随着运动学习而降低，（2）肌肉活动和共激活会与代谢能力的变化平行。坐着的受试者使用机械臂向目标进行水平平面到达运动。新的动力学涉及补偿粘性卷曲力场，扰动到达运动。在整个方案中连续测量代谢功率。受试者减少了运动错误，学习了新的动力学。到学习结束时，净代谢功率比初始学习降低了约20%（约0.1 W/kg）。肌肉活动和共激活也随着运动学习而减少。有趣的是，即使在肌肉活动和共激活已经稳定并且运动变化很小之后，代谢能力也发生了明显和显著的降低。这些结果提供了第一个证据，证明在运动学习和达到任务期间实际代谢减少。此外，他们认为肌肉活动可能无法像以前认为的那样完全解释代谢成本的变化。其他机制，如手臂肌肉活动的更细微特征，其他肌肉活动的变化和/或更有效的神经过程也可能是运动学习期间代谢成本降低的基础。
It is often assumed that the CNS controls movements in a manner that minimizes energetic cost. While empirical evidence for actual metabolic minimization exists in locomotion, actual metabolic cost has yet to be measured during motor learning and/or arm reaching. Here, we measured metabolic power consumption using expired gas analysis, as humans learned novel arm reaching dynamics. We hypothesized that (1) metabolic power would decrease with motor learning and (2) muscle activity and coactivation would parallel changes in metabolic power. Seated subjects made horizontal planar reaching movements toward a target using a robotic arm. The novel dynamics involved compensating for a viscous curl force field that perturbed reaching movements. Metabolic power was measured continuously throughout the protocol. Subjects decreased movement error and learned the novel dynamics. By the end of learning, net metabolic power decreased by similar to 20% (similar to 0.1 W/kg) from initial learning. Muscle activity and coactivation also decreased with motor learning. Interestingly, distinct and significant reductions in metabolic power occurred even after muscle activity and coactivation had stabilized and movement changes were small. These results provide the first evidence of actual metabolic reduction during motor learning and for a reaching task. Further, they suggest that muscle activity may not explain changes in metabolic cost as completely as previously thought. Additional mechanisms such as more subtle features of arm muscle activity, changes in activity of other muscles, and/or more efficient neural processes may also underlie the reduction in metabolic cost during motor learning.