Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60612, USA.
Cereb Cortex. 2009 Nov;19(11):2640-50. doi: 10.1093/cercor/bhp015. Epub 2009 Mar 2.
Gripping objects during everyday manual tasks requires the coordination of muscle contractions and muscle relaxations. The vast majority of studies have focused on muscle contractions. Although previous work has examined the motor cortex during muscle relaxation, the role of brain areas beyond motor cortex remains to be elucidated. The present study used functional magnetic resonance imaging to directly compare slow and precisely controlled force generation and force relaxation in humans. Contralateral primary motor cortex and bilateral caudate nucleus had greater activity during force generation compared with force relaxation. Conversely, right dorsolateral prefrontal cortex (DLPFC) had greater activity while relaxing force compared with generating force. Also, anterior cingulate cortex had greater deactivation while relaxing force compared with generating force. These findings were further strengthened by the fact that force output parameters such as the amplitude, rate, duration, variability, and error did not affect the brain imaging findings. These results demonstrate that the neural mechanisms underlying slow and precisely controlled force relaxation differ across prefrontal-striatal and motor cortical-striatal circuits. Moreover, this study demonstrates that the DLPFC is not only involved in slow and precisely controlled force generation, but has greater involvement in regulating slow and precisely controlled muscle relaxation.
在日常手工任务中抓住物体需要肌肉收缩和肌肉松弛的协调。绝大多数研究都集中在肌肉收缩上。尽管以前的工作已经研究了肌肉松弛期间的运动皮层，但运动皮层以外的大脑区域的作用仍有待阐明。本研究使用功能磁共振成像直接比较人类缓慢而精确控制的力量产生和力量松弛。与力量松弛相比，对侧初级运动皮层和双侧尾状核在力量产生期间具有更大的活性。相反，与产生力相比，右侧背外侧前额叶皮层（DLPFC）在放松力时具有更大的活性。此外，与产生力相比，前扣带皮层在放松力时具有更大的失活。这些发现进一步得到了以下事实的支持，即力输出参数（如振幅、速率、持续时间、变异性和误差）不会影响脑成像结果。这些结果表明，缓慢而精确控制的力量松弛的神经机制在额纹状体和运动皮质纹状体回路之间是不同的。此外，这项研究表明，DLPFC 不仅参与缓慢而精确的力量产生，而且在调节缓慢而精确的肌肉松弛方面具有更大的参与。
