Control of saccades in health and disease

描述(由申请人提供)：通常认为眼跳是弹道的和刻板印象的。然而，在启动对目标的扫视的运动指令中，存在结构化的可变性。我们认为，这种可变性在一定程度上反映了大脑与视觉刺激相关联的内部价值的系统性变化。也就是说，我们的大脑为我们的眼球运动目标分配一个值，这个相对值调节着移动我们眼睛的运动指令。如果这种可变性没有补偿，也就是说，如果眼跳是开环的，那么启动眼跳的运动命令的可变性将影响眼跳终点。然而，在健康人中，尽管启动眼跳的运动指令是不同的，但眼跳终点是准确的。我们认为，这是因为眼跳的控制强烈依赖于通过小脑的内部模型，监控发出的运动指令，并通过在眼跳轨迹的后期添加运动指令来有效地“控制”眼跳。只有当这个内部模型被校准时，补偿才是有效的，这将控制问题与适应问题联系起来。在这里，我们提出了一个控制眼跳的单一原则：运动的预期成本和回报由基底节评估，产生一个内部值来调节启动眼跳的运动指令。随着运动指令的产生，小脑监控它们并预测它们的感觉后果，产生调整，将运动引向目标。如果成功，我们的项目可能会通过将眼跳轨迹的可变性与预期回报和内部模型联系起来，从而在眼球运动研究中产生重大转变。这些概念已被证明是理解伸手等其他运动控制的基础。因此，我们或许能够就大脑如何控制运动产生一个单一的概念性框架。与公共健康相关：我们的目标是提出一种新的、连贯的理论，说明不同的大脑结构，如基底节和小脑，如何有助于控制眼跳。虽然小脑患者在他们的眼跳中表现出运动障碍，但我们的建议表明，运动障碍不是随机的，而是与大脑赋予视觉刺激的内在价值有关。基底节在运动控制中的作用仍然是一个深层次的谜团；我们的建议表明，这种结构与大脑赋予视觉刺激的内部价值之间可能存在联系，这一因素解释了引发眼跳的运动指令的一些变异性。

DESCRIPTION (provided by applicant): It is commonly assumed that saccades are ballistic and stereotypical. Yet, there is structured variability in the motor commands that initiate a saccade to a target. We propose that this variability is partly a reflection of a systematic change in the internal value that the brain associates with a visual stimulus. That is, our brain assigns a value to targets of our eye movements, and this relative value modulates the motor commands that move our eyes. If this variability was uncompensated, that is, if saccades were open-loop, then the variability in the motor commands that initiated the saccade would affect saccade endpoints. In healthy people, however, saccade endpoints are accurate despite the fact that the motor commands that initiate the saccade are variable. We suggest that this is because control of saccades is strongly dependent on internal models through the cerebellum, monitoring the outgoing motor commands and effectively `steering' the saccade by adding motor commands late in the saccade's trajectory. The compensation is effective only if this internal model is calibrated, which links the problem of control with adaptation. Here, we propose a single principle of control for saccades: Expected costs and rewards of a movement are evaluated by the basal ganglia, resulting in an internal value that modulates the motor commands that initiate the saccade. As the motor commands are generated, the cerebellum monitors them and predicts their sensory consequences, producing adjustments that steer the movement to the goal. If successful, our project may produce a major shift in oculomotor research by linking variability in trajectory of saccades with expected rewards and internal models. These concepts have proven fundamental in understanding control of other movements like reaching. As a result, we may be able to produce a single conceptual framework for how the brain controls movements in general. PUBLIC HEALTH RELEVANCE: Our aim is to produce a new, coherent theory of how various brain structures like the basal ganglia and the cerebellum contribute to control of saccades. While cerebellar patients exhibit dysmetria in their saccades, our proposal suggests that dysmetria is not random, but related to the intrinsic value that the brain assigns to the visual stimulus. The role of basal ganglia in control of movements has remained a deep puzzle; our proposal suggests that there may be a link between this structure and the internal value that the brain assigns to a visual stimulus, and that this factor accounts for some of the variability in the motor commands that initiate saccades.