Neural control of coordinated eye movements

项目总结/摘要 我们通过进行分离性扫视来观察位于3D视觉环境中的目标， 将目标图像投射到两个中央凹上。每次注视转移之后是用于视觉分析的注视期，在此期间， 必须保持新的聚散度水平。大多数研究都集中在控制共轭的电路上 眼跳，而分离眼跳和聚散眼运动的神经控制已收到较少 study.几个模型表明，外展运动神经元发送一个携带信息的单眼命令， 每只眼睛控制分离性扫视。其他模型也提出了扫视-聚散爆发的存在 投射到内直肌运动神经元并且仅在分离性扫视期间活跃的SVBN。我们 已经确定了这种新的细胞类型，它只在分离性扫视期间放电，在中央 中脑网状结构（cMRF）位于眼神经核（OMN）外侧。微电刺激 在cMRF的这个区域中，激活分离性扫视，而失活损害聚散凝视保持。 最近的解剖学发现表明，与近反应有关的运动前神经元位于 在cMRF中，并且它们投射到眼上区（SOA）和OMN。我们假设 cMRF，特别是SVBN，在分离性扫视的产生中起着关键作用。我们进一步 假设cMRF和SOA之间的投射形成了以前未描述的神经回路的一部分 产生聚散积分，允许在注视期间保持聚散角。其他解剖 和电生理研究结果表明，小脑，特别是尾顶核， 后间核在控制正常人和正常人的聚散眼运动中起作用， strabeberous个人。因此，我们假设小脑对cMRF/SOA复合体的输入有助于 编码或调节分离性扫视。在这些总体假设的指导下，我们提出了具体目标 来描述这个神经回路1.为了确定SVBN和cMRF在生产中的作用， 分离性扫视; 2.为了检验cMRF/SOA复合体是聚散度积分器的假设， 负责保持水平的收敛; 3.为了确定小脑的投射是如何 cMRF/SOA电路参与分离性扫视和聚散眼的产生 动作为了验证我们的假设，我们将使用已建立的神经生理学技术 （电生理记录，逆向激活，电微刺激和可逆 药理学调节）。我们项目的总体目标是大大增加我们对 神经回路控制灵长类动物的3D眼球运动，并广泛影响眼场，导致 新的神经生理学和建模方法。这些发现还将为以下方面提供重要依据： 理解在诸如斜视的眼球运动功能障碍中缺乏精确的双眼协调。

Project Summary / Abstract We look between targets located in the 3D visual environment by making disjunctive saccades that bring the target image onto both foveae. Each gaze shift is followed by a fixation period for visual analysis during which the new vergence level must be maintained. Most studies have focused on the circuitry controlling conjugate saccades, whereas the neural control of disjunctive saccades and vergence eye movements has received less study. Several models suggest that abducens motoneurons send a monocular command carrying information to each eye to control disjunctive saccades. Other models have proposed the existence of saccade-vergence burst neurons (SVBNs) that project to medial rectus motoneurons and are active only during disjunctive saccades. We have identified this novel cell type, which only discharge during disjunctive saccades, in the central mesencephalic reticular formation (cMRF) lateral to the oculomotor nucleus (OMN). Electrical microstimulation in this region of the cMRF elicits disjunctive saccades, whereas inactivation impairs vergence gaze holding. Recent anatomical findings have demonstrated that premotor neurons related to the near response are located in the cMRF, and that they project to the supraoculomotor area (SOA) and to the OMN. We hypothesize that the cMRF, and the SVBNs in particular, play a critical role in the generation of disjunctive saccades. We further hypothesize that projections between the cMRF and SOA form part of a previously undescribed neural circuit that produces vergence integration, allowing vergence angle to be maintained during fixation. Other anatomical and electrophysiological findings demonstrate that the cerebellum, specifically, the caudal fastigial nucleus and the posterior interposed nucleus, play a role in controlling vergence eye movements in both normal and strabismic individuals. We therefore hypothesize that the cerebellar input to the cMRF/SOA complex helps encode or modulate disjunctive saccades. Guided by these overarching hypotheses, we propose Specific Aims to characterize this neural circuitry. 1. To determine the role of SVBNs and the cMRF in the production of disjunctive saccades; 2. To test the hypothesis that the cMRF/SOA complex is the vergence integrator responsible for maintaining the level of convergence; 3. To determine how the cerebellar projections to the cMRF/SOA circuitry are involved in the generation of disjunctive saccades and vergence eye movements. To test our specific hypotheses, we will use established neurophysiological techniques (electrophysiological recordings, antidromic activation, electrical microstimulation and reversible pharmacological modulation). The overall goal of our project is to substantially increase our understanding of the neural circuitry controlling 3D eye movements in primates, and to broadly impact the oculomotor field, leading to new neurophysiological and modeling approaches. These findings will also provide a critical basis for understanding the absence of precise binocular coordination in eye movement dysfunctions such as strabismus.