Somatosensory Basis of Human Motor Learning

我研究的长期目标是了解人类中枢神经系统是如何产生自主运动和运动学习的。这里描述的研究计划的目标是测试这样一种想法，即运动学习不仅涉及运动行为和大脑运动区域的变化，还包括体感功能和体感神经处理的变化。运动学习不仅改变了我们的动作方式，也改变了我们处理和感知自己动作的方式。为期5年的目标是(1)测试当我们学习与环境中的对象交互时，体感感知会以系统的方式发生变化的想法，以及(2)测试这些影响在体感和运动脑区域的神经基础。我们将测试这样一种观点，即基于学习的体感变化将取决于对象是目标(要达到的东西)还是障碍。我们将测试这样一种假设，即与没有物体时相比，当物体是障碍物时，感知到的手的位置将从物体移开，并朝向目标。我们将测试这样一种想法，即在障碍物附近体感敏锐度会更高，而在目标附近会更小。有趣的是，在语音感知中，与离元音原型较远的元音(感知磁铁效应)相比，听者对靠近元音原型(语音目标)的元音的声学差异不那么敏感。这提出了一种有趣的可能性，即知觉空间的扭曲是一种与熟练的运动行为相关的普遍现象。我们还将测试皮质和节段(脊髓)对伴随运动学习而来的躯体感觉变化的贡献。我们将使用重复经颅磁刺激(RTMS)来探索在运动学习前后，几个涉及躯体感觉、动作和运动学习的皮质区域的作用，包括初级躯体感觉皮层SI和SII区，辅助运动区(SMA)，背侧和腹侧运动前皮质PMD和PMV，以及顶叶皮质。为了评估节段性反射调制的潜在作用，我们将使用H反射范式来评估运动学习前后反射兴奋性的变化，以及这些变化与感觉肢体位置的变化之间的关系。总而言之，越来越多的行为、神经生理学和神经成像研究的证据表明，运动技能的获得既涉及知觉学习，也涉及运动学习。运动学习改变了大脑的感知功能和感觉回路。这为运动学习提供了一种新的理论方法，其中知觉学习和感觉可塑性起着基础性的作用。更好地理解运动技能学习的感觉和运动决定因素可能会导致更好的脑机接口，如神经假肢，以及建造具有生物启发控制的拟人化机器人的新方法。

The long term goal of my research is to understand how the human central nervous system produces voluntary movement and motor learning. The goal of the research program described here is to test the idea that motor learning involves not only changes to motor behaviour and motor areas of the brain, but incorporates changes in somatosensory function and somatosensory neural processing as well. Motor learning changes not only how we move but how we process and perceive our own movements. The 5-yr objectives are (1) to test the idea that somatosensory perception changes in systematic ways when we learn to interact with objects in the environment, and (2) to test the neural basis of these effects in somatosensory and motor brain areas. We will test the idea that learning-based somatosensory changes will depend on whether an object is a target (something to be reached) or an obstacle. We will test the hypothesis that sensed hand position will shift away from an object when it is an obstacle, and towards targets, compared to when there is no object. We will test the idea that somatosensory acuity will be greater near obstacles, and less near targets. Interestingly, in speech perception, listeners are less sentitive to acoustic differences in vowels that sit close to a vowel prototype (a speech target) compared to those that sit farther away from the prototype (the perceptual magnet effect). This raises the interesting possibility that warping of perceptual space is a general phenomenon associated with skilled motor behaviour. We will also test the cortical and segmental (spinal) contributions to somatosensory change accompanying motor learning. We will use repetitive transcranial magnetic stimulation (rTMS) to probe the role of several cortical areas involved in somatosensation, action and motor learning, before and after motor learning, including primary somatosensory cortical areas SI and SII, supplementary motor area (SMA), dorsal and ventral premotor cortices PMd and PMv, and parietal cortical areas. To assess the potential role of segmental reflex modulation we will use an H-reflex paradigm to assess changes in reflex excitability before vs after motor learning, and how those changes correlate with changes in sensed limb position. In summary, there is accumulating evidence from behavioral, neurophysiological, and neuroimaging studies that the acquisition of motor skills involves both perceptual and motor learning. Motor learning changes perceptual function and the sensory circuits of the brain. This points to a new theoretical approach to motor learning in which perceptual learning and sensory plasticity play a fundamental role. A better understanding of the sensory as well as motor determinants of motor skill learning could lead to better brain-machine interfaces such as neuro-prosthetic arms, as well as new approaches to building anthropomorphic robots with biologically-inspired control.