Vestibular Lagena Structure and Function

描述（由申请人提供）：许多物种利用地球磁场进行导航已经被广泛记录，尽管探测的感觉机制仍然难以捉摸。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——耳蜗可能提供了答案。在鸟类和鱼类中，耳蜗上皮已被证明含有高含量的铁和锌，这些元素可以形成磁铁矿化合物（例如，Fe3O4），而其他两个前庭耳石器官（耳室和耳囊）则没有。x射线光谱学和磁力显微镜将用于检查耳石器官受体是否存在磁偶极子（目的1）。如果存在于蛛丝中，偶极子可以作为磁场中定向的生物物理传感器。lagena表面不同的受体毛细胞极化可以提供一个空间地图，lagena在这个地图上输入相对于地球主磁场的方向信号，本质上就像一个磁罗盘。lagena事件是否编码磁性空间信息将使用细胞外神经记录技术进行检查（目的2）。其他lagena事件可以在垂直头部平面上编码线性加速度。空间调谐和线性运动和磁场激活的动态特性将在lagena传入中进行检查，以确定lagena中是否存在多模态位置场（目标2）。从行为上讲，lagenar神经切断已被证明会破坏鸟类正常的归巢能力（Harada, 2002）。我们假设lagena参与了通过中枢神经元提供信息来构建地磁地图以用于空间导航。在最后的目标（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、前庭信号和视觉信号的整合是否以及如何促进导航和空间定位形成了一个令人兴奋的新研究方向，目前提出的研究代表了一个完整的第一步。

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.