Microsaccadic sampling of moving image information provides Drosophila hyperacute vision.
Microsaccadic sampling of moving image information provides Drosophila hyperacute vision.
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DOI：
10.7554/elife.26117
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发表时间：
2017-09-05
期刊：
影响因子：
7.7
通讯作者：
Takalo J
中科院分区：
文献类型：
--
作者：
Juusola M;Dau A;Song Z;Solanki N;Rien D;Jaciuch D;Dongre SA;Blanchard F;de Polavieja GG;Hardie RC;Takalo J
小苍蝇的眼睛不应该看到精细的图像细节。由于果蝇表现出扫视视觉行为，并且它们的复眼具有相对较少的小眼（采样点），因此它们的光感受器将产生模糊且粗糙的视网膜图像。在这里，我们证明果蝇看到的世界远比经典理论预测的要好。通过使用电生理学、光学和行为测定，我们发现 R1-R6 光感受器的及时编码能力最大化，以实现快速高对比度突发，这类似于它们在扫视行为期间的光输入。在太空中，R1-R6 能够以超出预测的运动模糊极限的扫视速度解析移动物体。我们的研究结果表明，难熔光转导和快速光机械感光器收缩如何共同锐化时空中移动物体的视网膜图像，从而实现超敏锐视觉，并解释这种微扫视信息采样如何超出复眼的光学极限。这些发现阐明了敏锐度如何取决于光感受器功能和眼球运动。果蝇有五只眼睛：两只大复眼用于支持视觉，加上三只较小的单晶状眼睛用于导航。每只复眼监视 180° 的空间，由大约 750 个单元组成，每个单元包含 8 个称为光感受器的光敏细胞。这种相对较宽的光感受器间距被认为限制了果蝇视觉的锐度或敏锐度。产生最敏锐视力的人类视网膜区域（眼睛后部的感光表面）包含的光感受器密度是其 500 倍。尽管人类和果蝇的眼睛设计不同，但其工作原理相同。如果我们或果蝇的目光完全稳定，当眼睛适应不变的视觉刺激时，世界就会逐渐从视野中消失。为了确保这种情况不会发生，动物不断地进行快速、自动的眼球运动，称为微扫视。这些可以刷新视网膜上的图像并防止其褪色。但尚不清楚为什么它们不会导致视力模糊。标准的视觉解释假设视网膜和大脑执行大部分所需的信息处理，而光感受器只是检测进入眼睛的光量。然而，Juusola、Dau、Song 等人。现在通过证明光感受器特别适合检测由于微扫视而进入眼睛的光的波动模式来挑战这个想法。此外，果蝇眼睛分辨小型移动物体的能力远远好于根据感光器间距预测的能力。光感受器非常适合处理眼球运动的发现改变了我们对昆虫视觉的理解。这些发现还反驳了 100 年来的教条，即光感受器的间距限制了复眼的视觉清晰度。需要进一步的研究来确定包括人类在内的其他动物视网膜中的光感受器是否具有类似的特性。
Small fly eyes should not see fine image details. Because flies exhibit saccadic visual behaviors and their compound eyes have relatively few ommatidia (sampling points), their photoreceptors would be expected to generate blurry and coarse retinal images of the world. Here we demonstrate that Drosophila see the world far better than predicted from the classic theories. By using electrophysiological, optical and behavioral assays, we found that R1-R6 photoreceptors’ encoding capacity in time is maximized to fast high-contrast bursts, which resemble their light input during saccadic behaviors. Whilst over space, R1-R6s resolve moving objects at saccadic speeds beyond the predicted motion-blur-limit. Our results show how refractory phototransduction and rapid photomechanical photoreceptor contractions jointly sharpen retinal images of moving objects in space-time, enabling hyperacute vision, and explain how such microsaccadic information sampling exceeds the compound eyes’ optical limits. These discoveries elucidate how acuity depends upon photoreceptor function and eye movements. Fruit flies have five eyes: two large compound eyes which support vision, plus three smaller single lens eyes which are used for navigation. Each compound eye monitors 180° of space and consists of roughly 750 units, each containing eight light-sensitive cells called photoreceptors. This relatively wide spacing of photoreceptors is thought to limit the sharpness, or acuity, of vision in fruit flies. The area of the human retina (the light-sensitive surface at back of our eyes) that generates our sharpest vision contains photoreceptors that are 500 times more densely packed. Despite their differing designs, human and fruit fly eyes work via the same general principles. If we, or a fruit fly, were to hold our gaze completely steady, the world would gradually fade from view as the eye adapted to the unchanging visual stimulus. To ensure this does not happen, animals continuously make rapid, automatic eye movements called microsaccades. These refresh the image on the retina and prevent it from fading. Yet it is not known why do they not also cause blurred vision. Standard accounts of vision assume that the retina and the brain perform most of the information processing required, with photoreceptors simply detecting how much light enters the eye. However, Juusola, Dau, Song et al. now challenge this idea by showing that photoreceptors are specially adapted to detect the fluctuating patterns of light that enter the eye as a result of microsaccades. Moreover, fruit fly eyes resolve small moving objects far better than would be predicted based on the spacing of their photoreceptors. The discovery that photoreceptors are well adapted to deal with eye movements changes our understanding of insect vision. The findings also disprove the 100-year-old dogma that the spacing of photoreceptors limits the sharpness of vision in compound eyes. Further studies are required to determine whether photoreceptors in the retinas of other animals, including humans, have similar properties.