Forward Models, the Cerebellum and Development

描述（由申请人提供）：为了在我们的一生中做出准确的动作，人们认为我们的大脑形成了我们身体和环境的内部模型。这些内部模型随着我们的身体和与我们互动的环境发生变化而适应。一种理论内部模型是前向模型（FM），它对我们的运动命令的感官结果进行预测，并为我们提供预测误差以驱动适应。虽然FMs被用于模拟运动适应的计算，但很少有实验试图找到FMs在大脑中的神经基础。此外，在适应过程中，我们目前没有方法来估计每次试验中电机输出的变化有多少是由于FMs的适应造成的。在这里，我们提出了一种新的方法，用它来量化在一个试验的基础上对FMs的适应达到。利用这种新方法，我们可以通过测试患者群体来寻找FMs的神经基质。研究暗示小脑是FMs最可能发生的位置，并证明小脑损伤导致适应缺陷。最近我们发现，小脑实验对象能够改变他们的运动输出，以响应逐渐引入的扰动。如果FMs依赖于小脑，那么应该存在小脑受试者运动输出正常变化而FMs异常变化的情况。我们的新实验方法将使我们能够检验这一预测。在发育过程中，小脑比大脑成熟得慢。这被怀疑是为什么幼儿表现出异常的运动适应模式的潜在原因，类似于小脑受试者。这与儿童比成年人更擅长学习的普遍观念背道而驰。我们假设，随着小脑的发育，适应性更强烈地依赖于FMs。除了健康对照外，对这些群体进行测试，将为FMs提供一个重要的新图景——它们是如何影响我们的运动的，它们的生物学基础，以及它们是如何在我们的大脑中存在的。

DESCRIPTION (provided by applicant): In order to make accurate movements throughout our lifetime, it is thought that our brain forms internal models of our body and our environment. These internal models adapt as our body and the environment that we interact with undergo changes. One type of theoretical internal model is a forward model (FM), which makes predictions about the sensory consequences of our motor commands, and provides us with prediction errors to drive adaptation. Though FMs are used computationally to model motor adaptation, there have been few experiments that have attempted to find the neural basis of FMs in the brain. Furthermore, during adaptation, we currently have no method with which to estimate how much of the change in the motor output from trial to trial is due to adaptation of FMs. Here, we present a new method with which to quantify adaptation of FMs on a trial-by-trial basis during reaching. Using this new method, we can look for the neural substrates of FMs by testing patient populations. Studies implicate the cerebellum as the most likely location for FMs, and demonstrate that cerebellar damage leads to deficits in adaptation. Recently we discovered that cerebellar subjects are able to change their motor output in response to a gradually introduced perturbation. If FMs depend on the cerebellum, then there should be scenarios in which cerebellar subjects show normal changes in motor output, with abnormal changes in FMs. Our new experimental method will allow us to test this prediction. During development, the cerebellum matures more slowly than the cerebrum. This is suspected to be the underlying reason for why young children show abnormal patterns of locomotor adaptation, resembling that of cerebellar subjects. This runs against the common belief that young children are better learners than adults. We hypothesize that with development of the cerebellum, adaptation relies more strongly on FMs. Testing these groups, in addition to healthy controls, will provide a significant new picture of FMs - how they affect our movements, their biological underpinnings, and how they come to exist in our brains. PUBLIC HEALTH RELEVANCE: This research is geared towards developing a deeper understanding of how people learn from movement errors. We hope to determine which area of the brain is responsible for this ability and how it develops through childhood. This will be important knowledge for the improvement of therapeutics relating to motor rehabilitation and developmental disorders.