Research Center for Movement Control and Neuroplasticity, K.U. Leuven, Belgium.
J Cogn Neurosci. 2011 Nov;23(11):3456-69. doi: 10.1162/jocn_a_00018. Epub 2011 Mar 31.
Unimanual motor tasks, specifically movements that are complex or require high forces, activate not only the contralateral primary motor cortex (M1) but evoke also ipsilateral M1 activity. This involvement of ipsilateral M1 is asymmetric, such that the left M1 is more involved in motor control with the left hand than the right M1 in movements with the right hand. This suggests that the left hemisphere is specialized for movement control of either hand, although previous experiments tested mostly right-handed participants. In contrast, research on hemispheric asymmetries of ipsilateral M1 involvement in left-handed participants is relatively scarce. In the present study, left- and right-handed participants performed complex unimanual movements, whereas TMS was used to disrupt the activity of ipsilateral M1 in accordance with a "virtual lesion" approach. For right-handed participants, more disruptions were induced when TMS was applied over the dominant (left) M1. For left-handed participants, two subgroups could be distinguished, such that one group showed more disruptions when TMS was applied over the nondominant (left) M1, whereas the other subgroup showed more disruptions when the dominant (right) M1 was stimulated. This indicates that functional asymmetries of M1 involvement during ipsilateral movements are influenced by both hand dominance as well as left hemisphere specialization. We propose that the functional asymmetries in ipsilateral M1 involvement during unimanual movements are primarily attributable to asymmetries in the higher-order areas, although the contribution of transcallosal pathways and ipsilateral projections cannot be completely ruled out.
单手运动任务，特别是复杂或需要高力量的运动，不仅会激活对侧初级运动皮层（M1），还会引起同侧 M1 的活动。这种同侧 M1 的参与是不对称的，即左手的运动控制比右手的运动控制更多地涉及左侧 M1。这表明左半球专门用于控制任何一只手的运动，尽管之前的实验大多测试了右利手参与者。相比之下，关于左利手参与者同侧 M1 参与的半球不对称性的研究相对较少。在本研究中，左利手和右利手参与者都进行了复杂的单手运动，而 TMS 则根据“虚拟损伤”方法用于干扰同侧 M1 的活动。对于右利手参与者，当 TMS 施加于优势（左）M1 时，会引起更多的干扰。对于左利手参与者，可以区分出两个亚组，即一组当 TMS 施加于非优势（左）M1 时会引起更多的干扰，而另一组当刺激优势（右）M1 时会引起更多的干扰。这表明同侧运动中 M1 参与的功能不对称受手优势以及左半球专门化的影响。我们提出，单手运动中同侧 M1 参与的功能不对称主要归因于高阶区域的不对称，尽管不能完全排除胼胝体通路和同侧投射的贡献。
