Auditory processing of descending neurons in the prothorax of a bush-cricket

在过去的二十年里，蟋蟀的听觉处理和歌曲识别引起了越来越多的兴趣。黑纹钩鲶的声学行为（雄虫鸣唱，雌虫应答，均进行趋声性）一直被研究到不同水平的感觉神经元和中间神经元水平上的行为神经基础。A.由于三个特征，nigrovittata是特别感兴趣的：（i）雄性和雌性产生具有不同载波频率的歌声，（ii）雄性和雌性产生具有不同时间模式的歌声，以及（iii）雄性歌声具有两个成分，其中一个成分用作物种的标识符，第二个成分用作短的反射式雌性应答的触发器。到目前为止，已经研究了几种局部前胸神经元、向脑的上行神经元和脑神经元。一组听觉神经元具有从前胸到后神经节（DN）的下行轴突，这在A. nigrovittata由于其在前胸神经节中的小突起使得细胞内记录困难。先前对局部神经元（DUM）的研究表明，在这种情况下，从索马记录是一个有前途的选择。初步研究表明，从索马成功记录和染色DN是可能的，并表明每侧至少存在七种不同的DN类型。该项目的目的是通过它们的形态和对声刺激的反应来表征下行神经元。这应该可以识别出与歌曲识别相关的潜在神经元。其中可能有一个神经元调谐到男性的歌曲，这可能会引发女性的回应歌曲，这是由中胸翅膀产生的反射，速度太快，无法通过大脑循环。另一些则对低频和振动有明显的反应，就像对其他蟋蟀物种所描述的那样。这将是有趣的知道，这些是否有选择性地响应同种的歌曲模式，因此，可能是相关的近距离通信。甚至其他人似乎对超声波反应良好-他们的特定属性可能有助于了解他们的潜在作用。阻断抑制的实验应该证明，是否锐化调谐发生所描述的其他听觉神经元，以及，但不是下行神经元。这是由观察到的IPSP样的膜电位的负偏转建议。

Auditory processing and song recognition in bush-crickets has gained increasing interest during the last twenty years. The species Ancistrura nigrovittata has been studied from their acoustic behavior (the male sings, the female replies, both perform phonotaxis) to the neuronal basis of that behavior on the level of sensory neurons and interneurons on various levels. A. nigrovittata is of special interest due to three features: (i) males and females produce songs with different carrier frequencies, (ii) males and females produce songs of different temporal patterns and (iii) the male song has two components, from which one serves as identifier for the species and the second as trigger for the short, reflex-like female reply. Several local prothoracic neurons, ascending neurons to the brain and brain neurons have been studied so far. One group of auditory neurons with a descending axon from the prothorax to posterior ganglia (DN) has been widely ignored in A. nigrovittata due to its small processes in the prothoracic ganglion making intracellular recordings difficult. A previous study on local neurons (DUM) has shown that recording from the soma is a promising alternative in such a situation. Preliminary studies have demonstrated, that it is possible to record and stain DN with success from their soma and have suggested the existence of at least seven different DN types on each side. The purpose of the project is to characterize descending neurons by their morphology and responses to acoustic stimuli. This should identify potentially relevant neurons for song recognition. Among these might be a neuron tuned to the male song, which might elicit the female reply song, which is produced reflex like by the mesothoracic wings and is too fast to loop via the brain. Others obviously respond to low frequencies and vibration, as described for other bush-cricket species. It would be interesting to know, whether these respond selectively to the conspecific song pattern and, therefore, might be relevant for close distance communication. Even others seem to respond well to ultrasound – their specific properties might help to understand their potential role. Experiments with blocking inhibition should demonstrate, whether sharpening of tuning occurs as described for other auditory neurons as well, but not for descending neurons. This is suggested by the observation of IPSP-like negative deflections of the membrane potential.