DECOMPOSITION OF GAZE SIGNAL INTO EYE AND HEAD COMMANDS

基于对头部约束动物的实验，过去的研究表明，许多皮质和皮质下区域在控制眼球跳动方面发挥了作用。例如，自那以后，人们实际上在无头注视转移期间对上丘的神经元进行了研究，发现其表现出的放电特性与眼头协调运动的相关性更好，而不仅仅是与眼睛部分相关。既然眼睛和头部提供了改变方向的独立手段，那么一个凝视信号如何控制两者的运动呢？由于不同的运动神经元支配眼外肌和颈部肌肉，凝视信号是否分解为眼睛和头部成分？如果是这样，这种分解是在哪里发生的，又是如何发生的？视线转移的准确性是否由监测眼睛和头部的耦合或独立贡献的反馈机制来维持？由于高层结构已经被证明编码凝视，必须使用自下而上的方法来寻找潜在的凝视分解部位(S)。因此，这项提议的目的是研究脑干爆裂、紧张性刺激、停顿和运动神经元对凝视转移的贡献。具体地说，这些细胞的神经活动最初将在相同幅度的注视转移(无头状态)和眼跳(头约束条件)期间被记录，同时系统地改变初始眼睛位置。然后，这些神经元的活动将通过微刺激和化学微注射而改变。后一项实验用来扰乱眼球运动系统，并测量其反馈机制所维持的准确性。因此，对所需的凝视信号如何导致眼头协调运动的功能理解将有助于深入了解患有眼球运动系统神经障碍的患者的潜在电路故障。

Based on experiments in head-restrained animals, past studies have implicated a role for many cortical and subcortical regions in the control of saccadic eye movements. Neurons in the superior colliculus, for example, have since been investigated during head-free gaze shifts actually and were found to exhibit discharge properties that are correlated better with the coordinated eye-head movements than just the ocular component. Since the eyes and the head provide independent means of changing orientation, how does one gaze signal control movements of both? Is the gaze signal decomposed into eye and head components since different motor neurons innervate extraocular and neck muscles? If so, where and how does this decomposition occur? Is the accuracy of gaze shifts maintained by feedback mechanisms that monitor the coupled or independent contributions of the eyes and head? As higher structures have already been shown to code gaze, a bottom-up approach must be used to search for potential site(s) of decomposition of gaze. The aims of this proposal are, therefore, to study the contributions of brainstem burst, tonic, pause and motoneurons to gaze shifts. Specifically, the neural activity of these cells will initially be recorded during gaze shifts (head-free condition) and saccades (head-restrained condition) of equal amplitude, while systematically varying initial eye position. Then, the activity in these neurons will be altered by microstimulation and chemical microinjections. This latter experiment serves to perturb the oculomotor system and measure the accuracy maintained by its feedback mechanisms. A functional understanding of how a desired gaze signal results in a coordinated eye-head movement will consequently provide insights into potential circuitry malfunctions in patients with neurological disorders of the oculomotor system.