Oliver Patricia, Tremblay François
School of Human Kinetics, Faculty of Health Sciences, University of Ottawa, Ottawa, ON, Canada.
Somatosens Mot Res. 2009 Jun;26(2):64-73. doi: 10.1080/08990220903178928.
In this study, we compared changes in corticomotor excitability under various task conditions engaging the index finger of each hand. Functional demands were varied, from simple execution to demanding sensory exploration. In a first experiment, we contrasted facilitation in the first dorsal interosseus (FDI) by monitoring changes in motor evoked potentials (MEPs) when participants (young adults, n = 18) performed either a simple button pressing (BP) task or a more demanding tactile exploration (TE) task (i.e., discrimination of raised letters). This experiment showed a large effect of task conditions (p < 0.01) on MEP amplitude but no effect of "Hand", while latency measurements were unchanged. In fact, MEPs were on average 40% larger during TE (2410 +/- 1358 microV) than during BP (1670 +/- 1477 microV). The two tasks produced, however, different patterns of electromyographic (EMG) activity, which could have accounted for some of the differences observed. A second experimental session involved a subset of participants (10/18) tested in third task condition: finger movement (FM). The latter task consisted of scanning a smooth surface with the tip of the index finger to reproduce the movements seen with the TE task. The addition of this third condition task confirmed that MEP facilitation seen during TE reflected task-specific influences and not differences in background EMG activity. These results, altogether, provide further insights into the effect of task conditions on corticomotor excitability. Our findings, in particular, stress the importance of behavioural context and tactile exploration in leading to selective increase in corticomotor excitability during finger movements.
在本研究中，我们比较了双手食指在各种任务条件下皮质运动兴奋性的变化。功能需求各不相同，从简单的执行到要求较高的感觉探索。在第一个实验中，我们通过监测参与者（年轻成年人，n = 18）执行简单按键（BP）任务或要求更高的触觉探索（TE）任务（即辨别凸起字母）时运动诱发电位（MEP）的变化，对比了第一背侧骨间肌（FDI）的易化情况。该实验表明任务条件对MEP波幅有显著影响（p < 0.01），但对“手”没有影响，而潜伏期测量结果未变。事实上，TE期间MEP平均比BP期间大40%（TE期间为2410±1358微伏，BP期间为1670±1477微伏）。然而，这两项任务产生了不同的肌电图（EMG）活动模式，这可能解释了观察到的一些差异。第二个实验环节涉及一部分参与者（10/18）在第三种任务条件下进行测试：手指运动（FM）。后一项任务包括用食指尖扫描光滑表面以重现TE任务中的动作。增加这第三种任务条件证实了TE期间观察到的MEP易化反映了特定任务的影响，而非背景EMG活动的差异。总的来说，这些结果为任务条件对皮质运动兴奋性的影响提供了进一步的见解。特别是，我们的研究结果强调了行为背景和触觉探索在导致手指运动期间皮质运动兴奋性选择性增加方面的重要性。
