Neurophysiology of Saccade Adaptation: The Role of Superior Colliculus

描述（由申请人提供）：运动适应在发展过程中改善我们的动作，在我们试图获得新技能时调整它们，并在受伤时修复它们。我们的长期目标是确定运动适应的神经机制，维持跳眼运动的准确性。大多数（如果不是全部的话）关于眼跳适应的神经生理学研究都使用了靶向性（反应性）眼跳，这是对突然出现的从中央凹脱落的目标做出的反应，这里称为眼跳的视网膜定位目标。对于瞄准扫视，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[也称为期望扫视向量]）是一致的。然而，扫视通常必须与其他扫视或其他类型的眼球运动相协调，这些运动可能会在扫视达到预期目标之前进行干预。这种中断分离了将要执行的扫视向量和它的视网膜复位目标，因此大脑必须执行空间更新来重新计算预期的扫视向量。我们使用双扫视任务（DST）进行的初步实验显示：(1)上丘（SC）中与扫视相关的神经元的扫视爆发受到视网膜定位目标的调节；(2)意想不到的是，即使两个扫视具有相同的初始运动错误，靶向扫视的适应也不会泛化，即转移到第二个扫视。这些发现使我们假设SC对目标扫视和需要空间更新的扫视使用不同的处理。我们将研究这种单独的加工对扫视适应的影响。我们将使用三种方法来检验这一假设：1。通过行为实验，根据目标扫视和第二扫视的适应特征及其向其他类型扫视的转移，推断出目标扫视和第二扫视的适应位点。2. 2 .单单元记录，以揭示特定于两种不同眼跳类型及其适应的SC活动的任何变化。微刺激和局部失活，以测试在不同的刺激条件下SC地形活动的差异

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.