Role of Parabigeminal Neucleus in Visuomotor Behavior

描述(申请人提供)：良好的视力需要一个眼球运动系统，该系统可以对感兴趣的视觉目标进行快速而准确的眼球运动，称为眼跳。要做到这一点，大脑必须有一个目标位置的内部表示。上丘(SC)是驱动眼睛的脑干回路的眼跳指令的主要来源，它通过位置代码编码目标定位和眼跳指标：与眼跳向量地图一起注册的位置的视网膜地图。双侧臂旁核(PBN)是中脑外侧边缘与SC相互连接的一小群细胞，它似乎也编码了靶位置，但编码的是一个速率代码。当猫在视觉上跟踪移动的物体时，它们主要依靠一系列追赶眼球来持续拦截它。初步研究表明，在追赶眼跳的间隔时间内，PBN细胞的放电频率与眼睛与潜在目标之间的距离或视网膜位置误差(RPE)成正比。在眼跳过程中，PBN活动突然变化到适合眼跳末端RPE的水平，对于视觉反馈来说，这种方式似乎太快了，这表明活动可能会被内部产生的信号重置，例如可重新设置的眼速积分器，或开环前馈信号。它与SC的强大解剖互连意味着，PBN主要通过在扫视间隔期间提供关于目标位置的连续信息来对扫视系统做出贡献。它是否对眼跳的动态或衡量标准有所贡献尚不清楚。由于SC位置代码必须在某个点被转换成比率代码以驱动眼部运动，因此PBN可以提供用于理解如何实现位置到比率代码转换的有用模型。该项目的目标包括更好地定义RPE编码的范围和拓扑结构，确定PBN活动是否提供当前参与的扫视目标的索引，检查PBN与SC的交互，调查在扫视期间重置PBN活动的信号的性质，以及检查PBN在预测跟踪运动目标中的作用。从历史上看，动眼生理和临床神经学之间存在着卓有成效的相互作用。PBN似乎是动眼神经系统的重要组成部分，它与动眼神经回路模型的结合将扩大这一有价值的交换。

DESCRIPTION (provided by applicant): Good vision requires an oculomotor system that can make rapid and accurate eye movements, called saccades, to visual targets of interest. To do this, the brain must have an internal representation of target location. The superior colliculus (SC), the main source of saccade commands to brainstem circuits driving the eyes, encodes target localization and saccade metrics by place codes: a retinotopic map of locations in register with a map of saccade vectors. It appears that the parabigeminal nucleus (PBN), a small cluster of cells on the lateral edge of the midbrain that is reciprocally interconnected with the SC, also encodes target location, but by a rate code. When cats visually track a moving object, they rely primarily on a series of catch-up saccades to continually intercept it. Preliminary studies have revealed that in the intervals between catch-up saccades, PBN cells fire at rates proportional to the distance between the eye and potential target, or retinal position error (RPE). During saccades, PBN activity abruptly changes to levels appropriate to RPE at saccade end in a fashion that seems too fast for visual feedback, suggesting that activity may be reset by an internally generated signal, such as a resettable integrator of eye velocity, or an open-loop feedforward signal. Its robust anatomical interconnections with the SC imply that the PBN primarily contributes to the saccade system by providing continuous information on target location during intersaccade intervals. Whether or not it contributes to the dynamics or metrics of the saccade is unknown. Since the SC place code must at some point be translated into a rate code to drive eye movements, the PBN may provide a useful model for understanding how a place-to-rate code translation can be accomplished. The goals of this project include better defining the range and topography of RPE encoding, determining if PBN activity provides an index of the currently attended saccade target, examining PBN interactions with the SC, investigating the nature of the signal that resets PBN activity during saccades, and examining the role of the PBN in predictive tracking of moving targets. Historically, there has been a productive interaction between oculomotor physiology and clinical neurology. The PBN appears to be an important part of the oculomotor system, and its incorporation into models of oculomotor circuits will extend this valuable interchange.