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），询问如何从耳石终器产生的前庭信号，检测水平和垂直加速度，用于激活颈部肌肉反射性地重新定位头部。颈部损伤每年影响100万美国人的生命，但我们才刚刚开始了解如何控制姿势反射，以保护颈部。这方面的进展受到了阻碍，部分原因是颈部肌肉组织的复杂性及其在重新定向凝视和反射性地稳定头部相对于身体的多重功能。前庭脊髓（VS）通路的神经丰富的会聚耳石输入。VS通路携带的信号 在身体的静态倾斜和线性平移过程中，双侧和双侧激活颈部肌肉。我们假设，颈部肌肉活动将表现出空间调谐时，倾斜和平移的组合施加在整个3-D空间的身体顺序。我们进一步假设颈部肌肉的空间调谐与前庭脊髓神经元的空间调谐反应有因果关系。为了验证这些假设，将在松鼠猴中进行实验，其中记录颈部肌肉的肌电图（EMG）和VS通路的神经活动。不同的倾斜和平移组合将在整个三维空间中施加在身体上。最初的实验将确定特定的颈部肌肉群在不同方向的倾斜和平移过程中是否表现出空间调谐。第二组 实验将确定在前庭核中记录的VS神经元在不同方向的倾斜和平移期间是否表现出空间调谐响应。VS神经元将通过逆向刺激在生理上鉴定。此外，将同时记录颈部EMG活动和VS神经元活动，以便可以使用尖峰触发平均（SpikeTA）来识别神经放电和EMG活动之间的功能关系。将每个颈部肌肉的空间调谐与被识别为与颈部肌肉功能相关的VS神经元的亚群的集体空间调谐特性（通过SpikeTA识别）进行比较。该分析将用于确定空间调谐的颈部EMG活动是否与VS通路的空间特性有因果关系。在最后的实验中，头部将被允许在平移的方向上移动，同时记录VS神经元的反应。平移的方向将基于最大激活神经元的方向来选择。这些数据将用于我们确定如何耳石信号的修改过程中执行colllic反射。这些实验的结果对于我们理解耳石信号如何影响头部在正常活动（如运动）中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.