Spatial Interaction of Otolith mediated Collic Reflexes

项目2，耳石介导的结肠反射的空间相互作用(Gdowski，PI)，询问来自耳石内脏的前庭信号如何被用来激活颈部肌肉，从而反射性地重新定位头部。颈部损伤每年影响100万美国人的生活，但我们才刚刚开始了解为了保护颈部而进化的姿势反射是如何被控制的。进展一直受到阻碍，部分原因是颈部肌肉系统的复杂性，以及它在重新定位凝视和反射性稳定头部相对于身体方面的多重功能。前庭脊髓(VS)通路由汇聚的耳石输入丰富地支配。VS通路携带的信号 在身体的静态倾斜和直线平移中，两侧和相互激活颈部肌肉。我们假设，当倾斜和平移的组合在整个3-D空间中顺序地施加在身体上时，颈部肌肉活动将显示出空间调节。我们进一步假设，颈部肌肉的空间调谐与前庭脊髓神经元反应的空间调谐存在因果关系。为了验证这些假设，实验将在松鼠猴子身上进行，记录下颈部肌肉的肌电(EMG)和VS通路的神经活动。倾斜和平移的不同组合将在整个3-D空间中施加在身体上。最初的实验将确定特定的颈部肌肉组在不同方向的倾斜和平移过程中是否表现出空间调节。第二套 实验将确定记录在前庭核团中的VS神经元在不同方向的倾斜和平移时是否表现出空间调谐反应。VS神经元将通过逆行刺激进行生理学鉴定。此外，颈部肌电活动和VS神经元活动将被同时记录，以便尖峰触发平均(SpikeTA)可以用于识别神经放电和EMG活动之间的功能关系。每个颈部肌肉的空间调谐将与被识别为与颈部肌肉功能相关的VS神经元亚群的集体空间调谐特性进行比较(通过SpikeTA识别)。这一分析将被用来确定空间调谐的颈部肌电活动是否与VS通路的空间属性相关。在最后的实验中，将允许头部在平移方向移动，同时记录VS神经元的反应。平移的方向将根据最大限度地激活神经元的方向来选择。这些数据将被我们用来确定耳石信号在COLLIC反射的执行过程中是如何改变的。这些实验的结果对于我们理解耳石信号在正常活动中如何影响头部的方向具有重要意义。

Project 2, Spatial interactions of otolith mediated collic reflexes (Gdowski, PI), asks how the vestibular signals arising from otolith endorgans, which detect horizontal and vertical acceleration, are used to activate neck muscles that reflexively reorient the head. Cervical injury affects 1 million U.S. lives annually, yet we are just beginning to understand how postural reflexes that evolved to protect the neck are controlled. Progress has been hampered, in part, because of the complexity of the neck musculature and its multiple functions in reorienting gaze and reflexively stabilizing the head with respect to the body. Vestibulospinal (VS) pathways are richly innervated by converging otolith inputs. The signals carried by the VS pathways bilaterally and reciprocally activate neck muscles during static tilts and linear translations of the body. We hypothesize that neck muscle activity will exhibit spatial tuning when combinations of tilt and translation are imposed on the body sequentially throughout 3-D space. We further hypothesize that the spatial tuning of neck muscles is causally related to the spatial tuning of responses of vestibulospinal neurons. To test these hypotheses experiments will be carried out in squirrel monkeys in which the electromyography (EMG) of neck muscles and neural activity of VS pathways are recorded. Different combinations of tilt and translation will be imposed on the body throughout 3-D space. Initial experiments will determine if specific groups of neck muscles exhibit spatial tuning during tilts and translations in different directions. The second set of experiments will determine if VS neurons, recorded in the vestibular nuclei, exhibit spatial tuned responses during tilts and translations in different directions. VS neurons will be identified physiologically by antidromic stimulation. In addition, neck EMG activity and VS neuron activity will be recorded simultaneously so that spike-triggered averaging (SpikeTA) can be used to identify functional relationships between neural discharge and EMG activity. The spatial tuning of each neck muscle will be compared to the collective spatial tuning properties of sub-populations of VS neurons identified as functionally-related to the neck muscle (identified through SpikeTA). This analysis will be used to determine if the spatially-tuned neck EMG activity are causally related to the spatial properties of VS pathways. In the final experiments, the head will be allowed to move in the direction of translation while the responses of VS neurons are recorded. The directions of translation will be chosen based upon direction that maximally activates the neuron. These data will used us to determine how otolith signals are modified during the execution of collic reflexes. The results of these experiments are significant to our understanding of how otolith signals influence the orientation of the head during normal activities such as locomotion.