Uncovering the cortical architecture of motor skill

从弹钢琴到扣衬衫扣子，熟练的手部动作几乎对每一项人类活动都至关重要。这个研究项目的主要目的是了解人类大脑是如何学习和产生复杂动作的。当我们在某项运动技能上发展专长时，我们的大脑会发生什么变化？目前的一些理论认为，整个运动模式（比如网球发球）在神经元（或神经细胞）之间的连接中变得根深蒂固，就像一首歌被存储在唱片上一样。然而，运动专家可以灵活地将较小的运动元素组合在一起，产生一种新的运动，比如钢琴家即兴演奏一段众所周知的旋律，这表明了一种不同的结构。我们的假设是，初级运动区域学习基本的运动元素，而次级运动区域存储更抽象的表征，然后激活一系列更简单的运动原语。为了测试这种神经表征，我们将使用一种称为功能磁共振成像（fMRI）的技术，观察人类志愿者在执行不同运动任务时的大脑活动。我们不只是研究大脑的哪些部分被激活了，而是研究这些区域内的精细活动模式。通过观察不同动作的活动模式之间的关系，我们可以了解这些动作是如何被表征的，也就是说，大脑区域是反映单个动作元素、执行的具体细节，还是代表更抽象的特征。发现人类大脑中这种表征的能力使我们能够理解运动技能专家（如音乐家或运动员）的大脑与新手的大脑有何不同；帮助我们评估和改进培训方案；并且有助于理解中风后运动功能的恢复，这在某种程度上涉及与最初的运动技能学习类似的过程。该研究项目还将提供新的见解，以了解为什么以及如何在运动练习中向大脑施加小电流（一种称为经颅直流电刺激的技术）能够改善健康人的技能学习。

From playing the piano to buttoning a shirt – skilled hand movements are essential to nearly every human activity. The main objective of this research program is to understand how the human brain learns and produces complex movements. What changes in our brains as we develop expertise in a motor skill? Some current theories propose that whole movement patterns (such as a tennis serve) become engrained in the connections between neurons (or nerve cells), much like the way in which a song is stored on a record. However, the flexibility with which motor experts can combine smaller movement elements to produce a novel movement, such as a pianist improvising on a well-known melody, suggest a different architecture. Our hypothesis is that primary motor areas learn elementary movement elements, whereas secondary motor areas store a more abstract representation that then activates sequences of simpler movement primitives. To test for such neural representations, we will observe the activity in the brains of human volunteers, using a technique called functional magnetic resonance imaging (fMRI), while they perform different movement tasks. Instead of just studying which parts of the brain are activated, we investigate the fine-grained patterns of activity within of these areas. By looking at the relationship between the activity patterns for different movements, we can learn how these movements are represented, i.e., whether the brain areas reflect single movement elements, specific details about the execution, or whether they represent more abstract characteristics. The ability to uncover such representations in the human brain allows us to understand how the brains of motor skill experts, such as musicians or athletes, differ from novices; helps us to evaluate and improve training protocols; and aids in understanding the recovery of motor function after stroke, which to some degree involves similar processes as initial motor skill learning. The research program will also provide new insights into why and how a small electric current applied to the brain during motor practice (a technique called transcranial direct current stimulation) is able to improve skill learning in healthy humans.