The Cerebellum as a State-Estimator for the Coordination of Skilled Movements

协调、巧妙的动作是人类神经系统的显著成就。虽然我们已经成功地建立了可以击败最好的人类棋手的计算机系统，但开发一个能够像新手一样优雅和轻松地拿起棋子并在棋盘上移动的人工系统一直是极其困难的。大脑如何产生协调的运动仍然是认知神经科学面临的一个重要挑战。部分答案将来自对小脑功能的了解，小脑功能是运动通路的一个重要组成部分。在国家科学基金会的支持下，加州大学伯克利分校的理查德·伊弗里博士和班戈威尔士大学的约恩·迪德里克森博士将开展一项多方面的研究计划，以加深我们对小脑在协调中的作用的理解。基于机器人领域的新理论见解，这项研究计划将集中评估两个假设：小脑功能是否最好被理解为控制电路的一部分，该电路基于来自其他肢体的感觉和运动信号来塑造对肌肉的运动命令？或者，这种结构对于产生关于我们行为的感官后果的预测是必不可少的，这一过程被称为状态估计？虽然人们早就认识到小脑功能障碍会导致失去熟练的运动能力，但共济失调的症状可能是由于控制不良、预测能力差或两者兼而有之。为了区分这些假设，参与者将被训练进行新颖的双手动作，其中一只手的运动将取决于对另一只手状态的准确预测。功能磁共振成像将用于确定小脑激活是否与状态估计或控制有关。成像工作将得到涉及单侧小脑损伤患者的研究的补充。这里的重点是比较状态估计或控制需要共济失调肢体的条件，提供关于这一结构对其中一种或两种功能的必要性的强有力的测试。鉴于我们的绝大多数日常活动--打字、开车、做饭--通常都需要协调我们两个上肢的动作，所以对双手技能的研究非常重要。目前的项目应该是为研究身体多个部位的协调(例如，协调头部、眼睛和手臂的运动)，甚至是不同个人之间的协调(例如，跳舞、篮球)而制定一般理论框架的重要一步。虽然研究计划侧重于小脑，但基本思想为探索熟练动作背后的神经机制提供了一般方法。该项目还将为本科生、研究生和博士后研究人员提供认知神经科学方面的研究培训机会。这项工作将把对工程学、心理学和神经科学感兴趣的学生聚集在一起，提供独特的跨学科培训机会，并增进我们对人类运动系统的理解。

Coordinated, skillful movements are remarkable achievements of the human nervous system. While we have succeeded in building computer systems that can beat the best human chess player, it has been extremely difficult to develop an artificial system that can pick up and move the chess pieces about the board with anything resembling the grace and ease of the novice chess player. How the brain produces coordinated movements remains an important challenge for cognitive neuroscience. Part of the answer will come from an understanding of cerebellar function, a prominent component of the motor pathways. With support from the National Science Foundation, Dr. Richard Ivry of the University of California, Berkeley and Dr. Jörn Diedrichsen of the University of Wales, Bangor, will pursue a multi-faceted research program to further our understanding of the role of the cerebellum in coordination. Building on new theoretical insights from the field of robotics, the research program will center on evaluating two hypotheses: Is cerebellar function best understood as part of the control circuitry that shapes the motor commands to the muscles based on sensory and motor signals from other limbs? Or is this structure essential for generating predictions concerning the sensory consequences of our actions, a process known as state estimation? While it has long been recognized that cerebellar dysfunction leads to a loss of skilled movement, the symptoms of ataxia may be due to poor control, poor prediction, or both. To distinguish among these hypotheses, participants will be trained to perform novel bimanual movements in which the movement of one hand will depend on an accurate prediction of the state of the other hand. Functional magnetic resonance imaging will be used to determine if cerebellar activation is related to state estimation or control. The imaging work will be complemented by studies involving patients with unilateral cerebellar damage. Here the focus is on a comparison between conditions in which the ataxic limb is required for either state estimation or control, providing strong tests concerning the necessity of this structure to one or both of these functions. The study of bimanual skills is important given that the vast majority of our daily actions -- typing, driving, cooking -- typically require coordinating the movements of our two upper limbs. The current project should serve as an important step in developing a general theoretical framework for studying coordination across multiple parts of the body (e.g., coordinating movements of the head, eyes, and arms), or even between different individuals (e.g., dancing, basketball). While the research plan focuses on the cerebellum, the basic ideas offer a general approach for exploring the neural mechanisms underlying skilled actions. This project will also provide research training opportunities in cognitive neuroscience for undergraduate, graduate, and post-doctoral researchers. The work will bring together students with interests in engineering, psychology, and the neurosciences, providing unique interdisciplinary training opportunities and advancing our understanding of the human motor system.