Vestibular Lagena Structure and Function

描述(申请人提供)：许多物种利用地球磁场进行导航已被广泛记录，尽管探测的感官机制仍然难以捉摸。最近的证据表明，在许多非哺乳动物脊椎动物中发现的第三种前庭耳石受体Lagena可能提供了答案。在鸟类和鱼类中，文昌鱼的耳石上皮含有大量的铁和锌，这些元素可以形成磁铁矿化合物(如Fe3O4)，而其他两个前庭耳石器官(椭圆囊和球囊)则不含铁和锌。将使用X射线光谱学和磁力显微镜检查耳石器官感受器是否存在磁偶极子(目标1)。如果出现在拉格纳，偶极子可以作为生物物理换能器在磁场中定位。然后，拉格纳表面不同的受体毛细胞极化可以提供一个空间地图，在该空间地图上，拉格纳传入相对于地球主场的定向信号方向，本质上起到磁罗盘的作用。将使用细胞外神经记录技术(目标2)来检查Lagena传入神经是否编码磁性空间信息。其他Lagena传入可能编码垂直头部平面中的线性加速度。将在Lagena传入中检查对直线运动和磁场激活的空间调谐和动力学特性，以确定Lagena中是否存在多峰位场(目标2)。行为上，脊神经切断已经被证明扰乱了鸟类的正常归巢能力(Harada，2002)。我们假设大脑角参与了中枢神经元提供信息以构建用于空间导航的地磁地图的过程。在最终目标(目标3)中，消融研究将使用行为取向范式检查对磁场检测的影响。磁罗盘、前庭和视觉信号的集成是否以及如何有助于导航和空间定位形成了一个令人兴奋的新研究方向，目前拟议的调查代表着一个完整的初始步骤。

DESCRIPTION (provided by applicant): The use of the Earth's magnetic field by many species for navigation has been widely documented although the sensory mechanism for detection remains elusive. Recent evidence suggests that the lagena, the third vestibular otolith receptor found in many non-mammalian vertebrates, may provide the answer. In birds and fish, the lagena epithelium has been shown to have a high content of iron and zinc, elements that could form magnetite compounds (e.g., Fe3O4), while the other two vestibular otolith organs (utricle and saccule) do not. X-ray spectroscopy and magnetic force microscopy will be used to examine the otolith organ receptor for the presence of magnetic dipoles (Aim 1). If present in the lagena, the dipoles could serve as a biophysical transducer for orientation in a magnetic field. Differing receptor hair cell polarizations across the lagena surface could then provide a spatial map upon which lagena afferents signal directions of orientation relative to the Earth main field, essentially acting as a magnetic compass. Whether lagena afferents encode magnetic spatial information will be examined using extracellular neural recording techniques (Aim 2). Other lagena afferents may encode linear accelerations in a vertical head plane. Both the spatial tuning and dynamic properties to linear motion and magnetic field activation will be examined in lagena afferents to determine if multimodal place fields exist in the lagena (Aim 2). Behaviorally, lagenar nerve section has been shown to disrupt normal homing ability in birds (Harada, 2002). We hypothesize that the lagena is involved in providing information to construct a geomagnetic map by central neurons for use in spatial navigation. In the final Aim (Aim 3), ablation studies will examine the effects upon magnetic field detection using behavioral orientation paradigms. Whether and how integration of magnetic compass, vestibular, and visual signals contribute to navigation and spatial orientation forms an exciting new direction of research that the current proposed investigation represents an integral initial step.