NASA Neurolab: Chronic Recording of Otolith Nerves in Microgravity

所有脊椎动物的重力接收很大程度上是由内耳前庭系统中称为耳石器官的结构完成的。这些器官是含有被称为耳石的致密钙化块的袋子；重力对这些块的作用覆盖着专门的机械感觉细胞，为确定正常的地球垂直方向提供了信号。这些耳石器官的神经活动表现为兴奋性和抑制性放电模式的组合，在某些情况下，大脑通过称为传出的神经纤维发出某种调制，影响传入的放电模式。关于妊娠器官长期活动的信息并不多。神经实验室的飞行提供了一个独特的机会来测试重力对远低于正常地球重力的力的响应，从而极大地扩大了测试关于重力信号神经编码的假说的研究范围。该项目使用一种新的电生理记录技术对自由移动的鱼进行比较，以比较在各种力范围内地面和空间对重力的反应。这项工作的结果将从根本上提供关于这个感觉系统的重要信息，并将产生从前庭神经科学到一般感官科学的影响，很可能对人类航天的应用方面具有重要意义。对该项目的贡献代表了NSF生物科学局参与了NASA/机构间神经实验室在航天飞机轨道上的活动，这反过来又是大脑活动十年的一部分。

Gravity reception in all vertebrate animals is done largely by structures called otolith organs in the vestibular system of the inner ear. These organs are pouches that contain dense calcified masses called otoliths; the action of gravity on these masses, overlying specialized mechanosensory cells, provides a signal for determining the normal earth-vertical direction. Nerve activity from these otolith organs show combinations of excitatory and inhibitory firing patterns, and under some conditions the brain sends some kinds of modulation by nerve fibers called efferents, which affect the incoming firing patterns. Not much information is available about long-term activity of gravistatic organs. The flight of Neurolab provides a unique opportunity to test gravitational responses to forces far less than normal earth gravity, and so greatly extend the study range for testing hypotheses about neural encoding of gravity signals. This project uses a novel electrophysiological recording technology in freely-moving fish to compare earth-based with space-based responses to gravity over a wide range of forces. Results from this work will provide fundamentally important information on this sensory system, and will have an impact beyond vestibular neuroscience to sensory science in general, and is likely to be important to applied aspects of human spaceflight. Contribution to this project represents the NSF Biological Sciences Directorate's participation in the NASA/Interagency Neurolab activity on the space shuttle orbiter, which in turn is part of Decade of the Brain activities.