Neurophysiology of Saccade Adaptation: The Role of Superior Colliculus

描述(申请人提供)：运动适应在发育过程中改进我们的动作，当我们试图获得一项新技能时调整它们，如果它们因受伤而受损则进行修复。我们的长期目标是确定维持眼跳运动准确性的运动适应的神经机制。大多数关于眼跳适应的神经生理学研究(如果不是全部的话)都使用了靶向(反应性)眼跳，以应对突然出现的目标从中心凹坠落，在这里被称为眼跳的视网膜目标。对于目标眼跳，视网膜定位目标的向量和初始运动误差(目标和当前眼睛位置之间的差[也称为所需的眼跳向量])是一致的。然而，眼跳通常必须与其他眼跳或其他类型的眼球运动相协调，这可能会在执行针对预期目标的眼跳之前进行干预。这样的干扰会将要执行的扫视的矢量与其视网膜目标分离，因此大脑必须执行空间更新来重新计算预期的扫视的矢量。我们使用双眼跳任务(DST)的初步实验表明：(1)上丘(SC)中与眼跳相关的神经元的扫视爆发受到视网膜目标的调制，(2)出人意料的是，靶向眼跳的适应并不能概括，即转移到DST的第二次眼跳，即使两次扫视具有相同的初始运动错误。这些发现使我们假设SC使用不同的处理来定位眼跳和需要空间更新的眼跳。我们将研究这种单独的处理对眼跳适应的影响。我们将使用三种方法来验证这一假设：1.行为实验根据靶向眼跳和DST的第二次眼跳的特点以及它向另一种类型的眼跳的迁移来推断目标眼跳和第二次眼跳的适应位置。2.单单位记录，以揭示两种不同眼跳类型特有的SC活动的任何变化及其适应；3.微刺激和局部失活，以测试SC地形图活动在 在这两个任务中执行扫视。由于猿猴和人类眼跳运动行为的相似性，本项目的研究结果对眼跳运动障碍患者的诊断、治疗和康复具有相当大的相关性。我们提出的实验旨在提供行为和神经生理学证据，证明在不同目标背景下产生的相同向量的眼跳适应不会相互转移，因此涉及不同的适应路径。了解在不同环境中眼跳之间的适应转移的限制可能有助于为眼跳障碍患者设计更具体的康复策略， 也许还有一般性的运动缺陷。

DESCRIPTION (provided by applicant): Motor adaptation refines our movements during development, adjusts them when we attempt to acquire a new skill, and repairs them if they are compromised by injury. Our long-term goal is to identify the neural mechanisms of the motor adaptation that maintains the accuracy of saccadic eye movements. Most, if not all, neurophysiological studies on saccade adaptation have used targeting (reactive) saccades made in response to the sudden appearance of a target that falls off the fovea, called here the retinotopic goal of the saccade. For targeting saccades, the vectors of the retinotopic goal and the initial motor error (the difference between the target and current eye positions [also called the desired saccade vector]) are congruent. However, saccades often must be coordinated with other saccades or other types of eye movement, which may intervene before a saccade to an intended goal is executed. Such interruptions dissociate the vector of the saccade to be executed and its retinotopic goal, so the brain must perform a spatial updating to re-compute the vector of the intended saccade. Our preliminary experiments using a double-saccade task (DST) revealed that (1) the saccadic burst of saccade-related neurons in the superior colliculus (SC) are modulated by the retinotopic goal, and (2) unexpectedly, adaptation of targeting saccades does not generalize i.e., transfer, to the second saccade of a DST, even when the two saccades have identical initial motor errors. These findings lead us to hypothesize that the SC uses different processing for targeting saccades and saccades that require spatial updating. We will examine the effect of this separate processing on saccade adaptation. We will use three approaches to test this hypothesis: 1. Behavioral experiments to infer the adaptation sites of targeting saccades and the second saccade of a DST on the basis of both the characteristics of each adaptation and its transfer to the other type of saccade. 2. single unit recording to reveal any changes in SC activity specific to the two different saccade types and their adaptations and 3. microstimulation and focal inactivation to test the difference of SC topographic activity during the execution of saccades in the two tasks . Because of the similarities of simian and human saccadic eye movement behavior, the results of this project should have considerable relevance in the diagnosis, treatment and rehabilitation of patients with saccadic eye movement disorders. Our proposed experiments aim to provide both behavioral and neurophysiological evidence that adaptation of saccades with the same vectors, but generated in different goal contexts, do not transfer to each other and hence involve different adaptation pathways. Understanding the limitation of the transfer of adaptation between saccades in different contexts may help to design a more specific repertoire of rehabilitation strategies for patients with saccade disorders, and perhaps general motor deficits.