Role of reafferent mechanisms in predictive interactions between head and eye movement.

进行平滑的追踪眼球运动来跟踪移动的物体，例如飞鸟，是一种熟悉的日常活动。这个过程涉及匹配眼睛的速度与目标的速度，从而最大限度地减少视网膜上图像的移动并减少模糊。这种预期的运动是必不可少的，使我们能够克服视觉处理的延迟，否则会损害跟踪能力。在此之前，我们已经展示了如何通过重复呈现相同的运动刺激来产生这种预期运动。这就产生了对即将发生的目标运动的高预期，并允许发展平滑的预期运动。这些预期眼球运动的速度与未来目标速度成正比，这意味着工作记忆被用来暂时存储从先前经验中收集的速度信息。当头部和眼睛一起跟踪时，已经发现头部的类似预期跟踪运动。我们以前在这一领域的所有工作都局限于跟踪沿水平轴沿着的简单运动。在拟议的实验中，我们计划研究系统如何在更现实的条件下运行，对象水平，垂直和朝向或远离观察者移动。我们将研究大脑如何发展对头部和眼睛运动的预期控制。我们还将通过使用功能性磁共振成像（fMRI）来记录人类受试者用眼睛执行可预测和不可预测跟踪任务时的大脑活动，以确定大脑的哪些区域参与了预期运动的存储和生成。特别是，我们打算调查大脑活动时，跟踪一系列这样的运动，其中每个组件有不同的速度和方向。序列学习是一种简单的运动编程形式，允许受试者学习重复的动作序列，例如打字。我们之前已经发现，受试者可以在简单的水平运动过程中学习产生预期的动作，但我们预计，当序列涉及水平和垂直运动时，需要更多的重复，因为这对工作记忆的要求更高。产生预期活动是正常运动行为的基础，在帕金森等运动障碍患者中经常受到干扰。的疾病或小脑变性。从拟议的实验结果将提供更多的了解运动控制，从而导致改进的诊断，监测药物治疗和康复。

Making smooth pursuit eye movements to track moving objects, such as a flying bird, is a familiar everyday activity. The process involves matching the speed of the eye to that of the target, thereby minimizing movement of the image on the retina and reducing blur. Such anticipatory movements are essential to allow us to overcome delays in visual processing, which otherwise impair tracking ability. Previously, we have shown how such anticipatory movements may be generated by using repeated presentations of identical motion stimuli. This creates a high expectancy of impending target motion and allows smooth anticipatory movements to be developed. The velocity of these anticipatory eye movements is proportional to future target velocity, implying that working memory is used to temporarily store velocity information gleaned from prior experience. Similar anticipatory tracking movements of the head have been found when tracking with head and eyes together. All our previous work in this area has been confined to tracking simple movements along the horizontal axis. In the proposed experiments we plan to investigate how the system operates in more realistic conditions where objects move horizontally, vertically and toward or away from the observer. We will investigate how the brain develops anticipatory control of head and eye movements. We will also determine which areas of the brain are involved in the storage and generation of anticipatory movements by using functional magnetic resonance imaging (fMRI) to record brain activity as human subjects carry out predictable and non-predictable tracking tasks with the eye. In particular, we intend to investigate brain activity when tracking a sequence of such movements in which each component has different speed and direction. Sequence learning is a simple form of motor programming that allows subjects to learn repetitive sequences of movements, such as typing. We have found previously that subjects can learn to generate anticipatory movements to sequences during simple horizontal movement after only one or two presentations, but we expect that when the sequences involve both horizontal and vertical movements more repetitions will be required, because this places greater demands on working memory. Generating anticipatory activity is fundamental to normal motor behaviour and is often disrupted in patients with motor disorders such as Parkinson?s disease or cerebellar degeneration. Findings from the proposed experiments will provide greater understanding of motor control and thus lead to improvements in diagnosis, monitoring of drug treatment and rehabilitation.