Comparative Investigations of neuronal integration processes along the auditory pathway in simple systems

我们的世界充满了物理刺激，这些刺激可以被感觉器官检测到，并被大脑评估。为了繁殖或生存，探测声波对许多动物来说是必不可少的。沿听觉通路的神经元通过耳传入纤维的突触输入来接收周围的声音。在简单的听觉系统中，只有低突触水平沿听觉通路到大脑，如在丛林蟋蟀，输入到前胸神经节是第一个重要的信号整合中心。这个级别的神经元反应是基于初级感觉神经元的尖峰，这些神经元编码声音的频谱和时间信息。虽然在蟋蟀的耳朵中，频率识别是由局部行波完成的，这一点已经被很好地理解了，但时间编码的动态仍在研究中，也是当前提案的一个重点。在这项比较研究中，我们将研究两种不同灌木蟋蟀的神经元整合。这两个物种在交配行为上表现出性别差异，比如趋声性，它们的耳朵形态也有明显不同。在一个物种中，黄蚕的听觉器官被广泛扩展，并提供了对行为重要的听觉输入，即听觉中央凹。共约110个轴突投射到前胸神经节。另一种被分析的物种，长足跖虫，只有大约45个轴突向前胸神经节发送投射，没有任何过度分布。我们的比较研究将探讨这两个物种的神经元整合过程，旨在了解建立听觉中央凹的优势。在这个项目中，我们使用前胸神经节的多电极和细胞内记录来研究小网络中局部场电位的神经元整合，这是由来自蟋蟀耳朵的声音诱导信号决定的，而这些信号又通过激光多普勒振动仪、细胞内记录和神经解剖学研究来研究。

Our world is full of physical stimuli that can be detected by sensory organs and evaluated by the brain. For reproduction or survival, the detection of sound waves is essential for many animals. Neurons along the auditory pathway are informed about surrounding sounds by synaptic inputs through afferent fibres of the ear. In simple hearing systems with only low synapse levels along the auditory pathway to the brain, such as in bushcrickets, the input to prothoracic ganglion is the first important signal integration centre. The neuronal response at this level is based on the spiking of primary sensory neurons that encode spectral as well as temporal information of the sound. While frequency discrimination in the ear, which is accomplished by tonotopical travelling waves, is well understood in bushcrickets, the dynamics of the temporal encoding is still under investigation and one focus of the current proposal. In this comparative study we will investigate the neuronal integration in two different bushcricket species. Both species show sex-specific differences in mating behavior, like phonotaxis and their ears feature significantly different morphologies. In one species, Ancylecha fenestrata, the hearing organ is extensively expanded and provides an overrepresentation of behaviorally important auditory input, an auditory fovea. In total about 110 axons project to the prothoracic ganglion. The other here analyzed species, Mecopoda elongata, has only about 45 axons sending projections to the prothoracic ganglion without any overrepresentation. Our comparative study will investigate the neuronal integration process in both species and aims to gain knowledge on the advantage to build up an auditory fovea. In this project we use multielectrode and intracellular recordings in the prothoracic ganglion to investigate the neuronal integration by local field potentials in a small network, which is determined by the sound-induced signals from the bushcrickets ear, which in turn are investigated by Laser Doppler Vibrometry, intracellular recordings and neuroanatomical studies.