Joesch Maximilian, Plett Johannes, Borst Alexander, Reiff Dierk F
Max Planck Institute for Neurobiology, Department of Systems and Computational Neurobiology, Am Klopferspitz 18, 81371 Martinsried, Germany.
Curr Biol. 2008 Mar 11;18(5):368-74. doi: 10.1016/j.cub.2008.02.022.
The crystalline-like structure of the optic lobes of the fruit fly Drosophila melanogaster has made them a model system for the study of neuronal cell-fate determination, axonal path finding, and target selection. For functional studies, however, the small size of the constituting visual interneurons has so far presented a formidable barrier. We have overcome this problem by establishing in vivo whole-cell recordings from genetically targeted visual interneurons of Drosophila. Here, we describe the response properties of six motion-sensitive large-field neurons in the lobula plate that form a network consisting of individually identifiable, directionally selective cells most sensitive to vertical image motion (VS cells). Individual VS cell responses to visual motion stimuli exhibit all the characteristics that are indicative of presynaptic input from elementary motion detectors of the correlation type. Different VS cells possess distinct receptive fields that are arranged sequentially along the eye's azimuth, corresponding to their characteristic cellular morphology and position within the retinotopically organized lobula plate. In addition, lateral connections between individual VS cells cause strongly overlapping receptive fields that are wider than expected from their dendritic input. Our results suggest that motion vision in different dipteran fly species is accomplished in similar circuitries and according to common algorithmic rules. The underlying neural mechanisms of population coding within the VS cell network and of elementary motion detection, respectively, can now be analyzed by the combination of electrophysiology and genetic intervention in Drosophila.
果蝇黑腹果蝇视叶的晶体状结构使其成为研究神经元细胞命运决定、轴突路径寻找和靶标选择的模型系统。然而，对于功能研究而言，构成视觉中间神经元的小尺寸迄今为止构成了巨大障碍。我们通过对果蝇经过基因靶向的视觉中间神经元进行体内全细胞记录克服了这一问题。在此，我们描述了小叶板中六个对运动敏感的大场神经元的反应特性，这些神经元形成了一个由个体可识别、对垂直图像运动最敏感的方向选择性细胞（VS细胞）组成的网络。单个VS细胞对视觉运动刺激的反应表现出所有表明来自相关类型基本运动检测器的突触前输入的特征。不同的VS细胞具有沿眼睛方位角顺序排列的独特感受野，这与它们在视网膜拓扑组织的小叶板中的特征细胞形态和位置相对应。此外，单个VS细胞之间的横向连接导致感受野强烈重叠，其宽度比根据其树突输入预期的要宽。我们的结果表明，不同双翅目果蝇物种的运动视觉是通过相似的电路并根据共同的算法规则实现的。现在可以通过果蝇中电生理学和基因干预的结合来分别分析VS细胞网络内群体编码和基本运动检测的潜在神经机制。
