Neuronal processing of sky compass information in the brain of bees

许多动物都有一个有时间补偿的太阳指南针，这使它们能够推断出一个固定的地球方向。从不断变化的太阳方位角到鸟巢。太阳光在大气中的散射导致颜色渐变和沿天空的偏振光图案。这两种现象在空间上都与太阳方位角直接相关。因此，除了可以直接看到太阳之外，还可以利用它们来推断太阳的方位。六十多年来，蜜蜂一直被用作行为实验中天空罗盘定向的模式生物。然而，到目前为止，这种令人着迷的行为背后的神经基础仍然是个谜。这个项目的目标是利用神经生理学技术阐明蜜蜂大脑中与航行相关的极化和彩色视觉线索的处理过程。由于可获得的行为数据丰富，它们的大脑相当简单(与脊椎动物相比)，以及将这些动物留在户外的独特可能性，即在自然光条件下，蜜蜂与其他物种不同，它们适合进行这些实验。两个问题构成了这项提案的核心。1.偏振和非偏振光刺激在这些动物的大脑中是如何整合的？2.天空罗盘系统的动力学特性(包括昼夜节律和毫秒-S时间尺度)是什么？在天空罗盘导航过程中，大脑必须解决一项高度复杂的任务。一方面，关于太阳方位角的所有可用信息都必须被整合(偏振光刺激的方向、非偏振光刺激的方位和颜色)。另一方面，动物必须能够在任何时候区分太阳、天空和云。例如，当太阳本身不可见时，阳光下的云不应被错误地解释为太阳。通过使用不同的偏振光和非偏振光刺激，将通过细胞内记录来阐明其潜在的机制。在项目的第二部分，将研究天空罗盘系统神经元的长期和短期变化。钙成像和细胞外记录将被用来监测日常变化和神经活性物质对这些变化的影响。使用细胞内记录将使我能够研究通过动态视觉刺激引起的神经元调谐的短期变化，就像在飞行中所经历的那样。这个项目的结果将提供对基本神经原理的洞察，潜在的感觉处理与导航相关的视觉刺激。

Many animals possess a time-compensated sun compass, which enables them to infer a fixed earthbound direction, eg. to a nest, from the continually changing solar azimuth. Scattering of sun light in the atmosphere leads to a color gradient and a pattern of polarized light along the sky. Both phenomena are spatially directly linked to the solar azimuth. In addition to the direct view of the sun, they can therefore be exploited to infer the solar azimuth. For more than six decades, bees have been used as model organisms for sky compass orientation in behavioral experiments. However, the neuronal basis underlying this fascinating behavior has so far remained enigmatic. The goal of this project is to elucidate the processing of navigationally relevant polarized and chromatic visual cues in the brain of bees, using neurophysiological techniques. Due to the abundance of behavioral data available, their rather simple brain (compared to vertebrates), and the unique possibility to keep these animals outdoors, i.e. under natural light conditions, bees lend themselves to these experiments like no other species. Two questions form the core of this proposal. 1. How are polarized and unpolarized light stimuli integrated in the brain of these animals? 2. What are the dynamic properties (both circadian and on the ms-s timescale) of the sky compass system? During sky compass navigation, the brain has to solve a highly sophisticated task. On one hand, all available pieces of information regarding solar azimuth have to be integrated (orientation of polarized light stimuli, azimuth and color of unpolarized light stimuli). On the other hand the animal has to be able to differentiate between sun, sky, and clouds at all times. For example when the sun itself is not visible a sunlit cloud should not be erroneously interpreted as the sun. By stimulation with different polarized and unpolarized light stimuli the underlying mechanisms will be elucidated using intracellular recordings. In the second part of the project, long- and short-term changes of neurons of the sky compass system will be investigated. Calcium imaging and extracellular recordings will be used to monitor diurnal changes and the influence of neuroactive substances on these. Using intracellular recordings will allow me to investigate short-term changes in neuronal tuning that are elicited through dynamic visual stimuli, as experienced during flight. The outcome of this project will provide insight into fundamental neuronal principles underlying sensory processing of navigationally relevant visual stimuli.