Wernitznig Stefan, Rind F Claire, Zankel Armin, Bock Elisabeth, Gütl Daniel, Hobusch Ulrich, Nikolic Manuela, Pargger Lukas, Pritz Elisabeth, Radulović Snježana, Sele Mariella, Summerauer Susanne, Pölt Peter, Leitinger Gerd
Research Unit Electron Microscopic Techniques, Division of Cell Biology, Histology and Embryology, Gottfried Schatz Research Center, Medical University of Graz, Graz, Austria.
Newcastle University, Biosciences Institute, Newcastle upon Tyne, UK.
J Comp Neurol. 2022 Feb;530(2):518-536. doi: 10.1002/cne.25227. Epub 2021 Aug 12.
The ability of locusts to detect looming stimuli and avoid collisions or predators depends on a neuronal circuit in the locust's optic lobe. Although comprehensively studied for over three decades, there are still major questions about the computational steps of this circuit. We used fourth instar larvae of Locusta migratoria to describe the connection between the lobula giant movement detector 1 (LGMD1) neuron in the lobula complex and the upstream neuropil, the medulla. Serial block-face scanning electron microscopy (SBEM) was used to characterize the morphology of the connecting neurons termed trans-medullary afferent (TmA) neurons and their synaptic connectivity. This enabled us to trace neurons over several hundred micrometers between the medulla and the lobula complex while identifying their synapses. We traced two different TmA neurons, each from a different individual, from their synapses with the LGMD in the lobula complex up into the medulla and describe their synaptic relationships. There is not a simple downstream transmission of the signal from a lamina neuron onto these TmA neurons; there is also a feedback loop in place with TmA neurons making outputs as well as receiving inputs. More than one type of neuron shapes the signal of the TmA neurons in the medulla. We found both columnar and trans-columnar neurons connected with the traced TmA neurons in the medulla. These findings indicate that there are computational steps in the medulla that have not been included in models of the neuronal pathway for looming detection.
蝗虫检测逼近刺激并避免碰撞或捕食者的能力取决于其视叶中的一个神经回路。尽管在过去三十多年里对其进行了全面研究，但关于该回路的计算步骤仍存在一些主要问题。我们利用飞蝗的四龄幼虫来描述小叶复合体中的小叶巨运动检测器1（LGMD1）神经元与上游神经纤维髓质之间的连接。使用连续块面扫描电子显微镜（SBEM）来表征被称为跨髓传入（TmA）神经元的连接神经元的形态及其突触连接。这使我们能够在识别突触的同时，在髓质和小叶复合体之间追踪数百微米长的神经元。我们从两个不同个体中追踪了两种不同的TmA神经元，从它们在小叶复合体中与LGMD的突触一直向上追踪到髓质，并描述了它们的突触关系。从薄板神经元到这些TmA神经元并没有简单向下游的信号传递；TmA神经元在接收输入的同时也会产生输出，存在一个反馈回路。不止一种类型的神经元塑造了髓质中TmA神经元的信号。我们发现髓质中与被追踪的TmA神经元相连的既有柱状神经元也有跨柱状神经元。这些发现表明，髓质中存在一些计算步骤尚未被纳入用于逼近检测的神经通路模型中。
