Circuits - Computation - Models, Max Planck Institute of Neurobiology, Am Klopferspitz 18, Martinsried 82152, Germany.
Circuits - Computation - Models, Max Planck Institute of Neurobiology, Am Klopferspitz 18, Martinsried 82152, Germany.
Curr Biol. 2018 Dec 17;28(24):4037-4045.e5. doi: 10.1016/j.cub.2018.11.010. Epub 2018 Dec 6.
Moving animals experience constant sensory feedback, such as panoramic image shifts on the retina, termed optic flow. Underlying neuronal signals are thought to be important for exploratory behavior by signaling unintended course deviations and by providing spatial information about the environment [1, 2]. Particularly in insects, the encoding of self-motion-related optic flow is well understood [1-5]. However, a gap remains in understanding how the associated neuronal activity controls locomotor trajectories. In flies, visual projection neurons belonging to two groups encode panoramic horizontal motion: horizontal system (HS) cells respond with depolarization to front-to-back motion and hyperpolarization to the opposite direction [6, 7], and other neurons have the mirror-symmetrical response profile [6, 8, 9]. With primarily monocular sensitivity, the neurons' responses are ambiguous for different rotational and translational self-movement components. Such ambiguities can be greatly reduced by combining signals from both eyes [10-12] to determine turning and movement speed [13-16]. Here, we explore the underlying functional logic by optogenetic HS cell manipulation in tethered walking Drosophila. We show that de- and hyperpolarization evoke opposite turning behavior, indicating that both direction-selective signals are transmitted to descending pathways for course control. Further experiments reveal a negative effect of bilaterally symmetric de- and hyperpolarization on walking velocity. Our results are therefore consistent with a functional architecture in which the HS cells' membrane potential influences walking behavior bi-directionally via two decelerating pathways.
运动中的动物会不断接收到感官反馈，例如视网膜上的全景图像移动，即光流。人们认为，潜在的神经元信号对于探索性行为很重要，因为它们可以指示意外的路线偏差，并提供关于环境的空间信息[1,2]。特别是在昆虫中，与自身运动相关的光流的编码已经得到很好的理解[1-5]。然而，对于相关神经元活动如何控制运动轨迹，仍存在理解上的差距。在果蝇中，属于两组的视觉投射神经元对全景水平运动进行编码：水平系统（HS）细胞对从前到后的运动产生去极化反应，对相反的方向产生超极化反应[6,7]，而其他神经元具有镜像对称的反应模式[6,8,9]。由于主要具有单眼敏感性，神经元的反应对于不同的旋转和平移自身运动分量是模棱两可的。通过结合双眼的信号[10-12]来确定转弯和运动速度[13-16]，可以大大减少这种模糊性。在这里，我们通过在系留行走的果蝇中进行光遗传 HS 细胞操作来探索潜在的功能逻辑。我们表明，去极化和超极化会引起相反的转弯行为，这表明两个方向选择性信号都被传递到下降途径以进行路线控制。进一步的实验表明，双侧对称的去极化和超极化对步行速度有负面影响。因此，我们的结果与一种功能架构一致，即 HS 细胞的膜电位通过两个减速途径双向影响步行行为。
