Department of Aerospace Engineering, University of Bristol, University Walk, Bristol BS8 1TR, UK.
Department of Zoology, University of Oxford, Oxford OX1 3PS, UK
Proc Biol Sci. 2017 Oct 11;284(1864). doi: 10.1098/rspb.2017.1622.
Flying insects use compensatory head movements to stabilize gaze. Like other optokinetic responses, these movements can reduce image displacement, motion and misalignment, and simplify the optic flow field. Because gaze is imperfectly stabilized in insects, we hypothesized that compensatory head movements serve to extend the range of velocities of self-motion that the visual system encodes. We tested this by measuring head movements in hawkmoths responding to full-field visual stimuli of differing oscillation amplitudes, oscillation frequencies and spatial frequencies. We used frequency-domain system identification techniques to characterize the head's roll response, and simulated how this would have affected the output of the motion vision system, modelled as a computational array of Reichardt detectors. The moths' head movements were modulated to allow encoding of both fast and slow self-motion, effectively quadrupling the working range of the visual system for flight control. By using its own output to drive compensatory head movements, the motion vision system thereby works as an adaptive sensor, which will be especially beneficial in nocturnal species with inherently slow vision. Studies of the ecology of motion vision must therefore consider the tuning of motion-sensitive interneurons in the context of the closed-loop systems in which they function.
飞行昆虫使用补偿性头部运动来稳定注视。与其他光动反应一样，这些运动可以减少图像位移、运动和失准，并简化光流场。由于昆虫的注视不能完美地稳定，我们假设补偿性头部运动有助于扩大视觉系统编码的自身运动速度范围。我们通过测量 respond to full-field visual stimuli of differing oscillation amplitudes, oscillation frequencies and spatial frequencies 的 Hawk 蛾对不同振荡幅度、振荡频率和空间频率的全视野视觉刺激的头部运动来检验这一点。我们使用频域系统识别技术来描述头部的滚动响应，并模拟了这将如何影响运动视觉系统的输出，该系统建模为计算的 Reichardt 检测器阵列。飞蛾的头部运动被调制，以允许编码快速和慢速的自我运动，有效地将视觉系统的工作范围扩大了四倍，以用于飞行控制。通过使用自己的输出来驱动补偿性头部运动，运动视觉系统因此作为一个自适应传感器工作，这对于具有内在缓慢视觉的夜间物种尤其有益。因此，对运动视觉生态学的研究必须考虑在它们发挥作用的闭环系统中运动敏感中间神经元的调谐。
