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

协调、熟练的动作是人类神经系统的卓越成就。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，但开发一种能够像新手棋手那样优雅而轻松地在棋盘上捡起棋子并移动棋子的人工系统是极其困难的。大脑如何产生协调运动仍然是认知神经科学的一个重要挑战。部分答案将来自对小脑功能的理解，小脑是运动通路的重要组成部分。在美国国家科学基金会的支持下，加州大学伯克利分校的Richard Ivry博士和威尔士大学班戈分校的Jörn Diedrichsen博士将开展一项多方面的研究计划，以进一步了解小脑在协调中的作用。以机器人领域的新理论见解为基础，该研究项目将集中于评估两个假设：小脑的功能是否最好地理解为控制电路的一部分，该电路根据来自其他肢体的感觉和运动信号向肌肉发出运动命令？或者这种结构对于产生关于我们行为的感官结果的预测（称为状态估计的过程）是必不可少的吗？虽然人们早就认识到小脑功能障碍会导致熟练运动的丧失，但共济失调的症状可能是由于控制不良、预测不良或两者兼而有之。为了区分这些假设，参与者将被训练进行新的双手运动，其中一只手的运动将依赖于对另一只手状态的准确预测。功能性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。影像学工作将通过涉及单侧小脑损伤患者的研究加以补充。这里的重点是在状态估计或控制需要共济肢体的条件之间的比较，提供关于该结构对这些功能中的一个或两个的必要性的强有力的测试。考虑到我们绝大多数的日常活动——打字、开车、做饭——通常需要协调我们两个上肢的运动，对双手技能的研究很重要。当前的项目应该作为一个重要的步骤，为研究身体多个部位的协调（例如，头部、眼睛和手臂的协调运动），甚至是不同个体之间的协调（例如，跳舞、篮球），发展一个通用的理论框架。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。本项目还将为本科生、研究生和博士后提供认知神经科学的研究培训机会。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，并促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.