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运动，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），它预测我们的运动指令的感官后果，并为我们提供预测误差以驱动适应。虽然FM在计算上被用来模拟运动适应，但很少有实验试图找到FM在大脑中的神经基础。此外，在适应过程中，我们目前还没有方法来估计从一次试验到另一次试验的运动输出变化中有多少是由于FM的适应。 在这里，我们提出了一种新的方法，量化适应FM在一个试验的基础上达到。使用这种新方法，我们可以通过测试患者群体来寻找FM的神经基质。研究暗示小脑是FM最可能的位置，并证明小脑损伤导致适应缺陷。最近，我们发现小脑受试者能够改变他们的运动输出，以响应逐渐引入的扰动。如果FM依赖于小脑，那么应该有小脑受试者在运动输出方面表现出正常变化，而FM则出现异常变化的情况。我们的新实验方法将使我们能够验证这一预测。 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根本原因，类似于小脑受试者。这与人们普遍认为的幼儿比成年人更善于学习的观点背道而驰。我们假设，随着小脑的发展，适应更强烈地依赖于FM。除了健康对照组之外，对这些群体进行测试将为FM提供一个重要的新画面-它们如何影响我们的运动，它们的生物基础以及它们如何存在于我们的大脑中。

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.