Neural Integration of Eye and Head Movements

描述（由申请人提供）：研究计划的长期目标是了解多个运动系统的神经整合。长期以来，眼神经系统一直是研究运动神经控制的模型。然而，在自然环境中，定向反应由多个眼球运动和骨骼运动动作组成，它们结合在一起形成一个复杂而协调的运动。科学研究的理想综合行动是协调的眼头运动，因为它建立在我们对眼神经系统的先进知识之上。该研究还提供了由眼、前庭和颈椎疾病引起的空间定向缺陷的诊断价值。 最近的实验表明，熟悉的眼神经结构，如上级丘（SC）和脑桥延髓网状结构（PMRF），输出一个电机命令，以取代视线（视线转移）所需的幅度和方向。视线转移可以作为协调的眼-头运动来执行，这意味着这些眼神经结构的输出也控制支配颈部肌肉的前运动回路。神经放电和眼外运动神经元之间的关联是通过记录头部受限扫视期间的活动来证明的。相比之下，尖峰和颈部运动神经元之间的关系只能通过观察协调的眼-头运动期间的活动来推断。由于在一般情况下，协调运动的眼睛和头部分量在时间上是相关的，因此还没有对具有头部运动的活动进行直接评估。因此，提出了四个具体的目标来表征活动和识别与头部运动控制相关的神经元。使用开发用于将头部运动与扫视眼球运动暂时分离的行为任务，将记录SC神经元的头部运动相关活动，无论是在不需要凝视转移时（特定目标1）还是在计划或执行凝视转移时（特定目标2）。将采用类似的操作来研究PMRF神经元的分布，PMRF神经元编码仅眼睛、仅头部和协调的眼-头运动（具体目标3）。最后，解剖技术将被用来确定SC神经元是否发送发散轴突侧支或分离的投影到PMRF的眼和头部控制区域（具体目标4）。

DESCRIPTION (provided by applicant): The long-term objective of the research program is to understand the neural integration of multiple motor systems. The oculomotor system has long served as a model for the study of neural control of movement. In the natural environment, however, an orienting response consists of multiple oculomotor and skeletomotor actions combined to form a complex yet coordinated movement. An integrated action ideal for scientific investigation is a coordinated eye-head movement because it builds on our advanced knowledge of the oculomotor system. The research also offers diagnostic value for spatial orientation deficits resulting from oculomotor, vestibular and cervical disorders. Recent experiments suggest that familiar oculomotor structures, such as the superior colliculus (SC) and pontomedullary reticular formation (PMRF), output a motor command to displace the line of sight (gaze shift) by a desired amplitude and direction. The gaze shift can be executed as a coordinated eye-head movement, implying that the outputs of these oculomotor structures also control premotor circuits that innervate the neck muscles. An association between neural discharge and extraocular motor neurons is demonstrated by recording activity during head-restrained saccades. In contrast, a relationship between spikes and neck motor neurons is only inferred by observing activity during coordinated eye-head movements. A direct evaluation of the activity with head movements has not been performed yet because, under ordinary circumstances, the eye and head components of the coordinated movement are temporally correlated. Hence, four specific aims are proposed to characterize activity and identify neurons associated with head movement control. Using behavioral tasks developed to temporally uncouple head movements from saccadic eye movements, SC neurons will be recorded for head movement related activity, both when no gaze shift is required (Specific Aim 1) and when a gaze shift is planned or being executed (Specific Aim 2). Similar manipulations will be employed to investigate the distribution of PMRF neurons that encode eye-only, head-only and coordinated eye-head movements (Specific Aim 3). Finally, anatomical techniques will be used to determine whether SC neurons send divergent axon collaterals or segregated projections to the eye and head control regions of PMRF (Specific Aim 4).