Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, China.
Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, China; Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford OX1 3PT, UK.
Curr Biol. 2023 Aug 7;33(15):3179-3191.e4. doi: 10.1016/j.cub.2023.06.046. Epub 2023 Jul 11.
The ability to determine the distance to objects is an important feature of most visual systems, but little is known about the neuronal mechanisms for distance estimation. Larval zebrafish execute different visual behaviors depending on distance; at medium distances, they converge their eyes and approach, but when the prey is close enough, they execute a strike and suck the prey into their mouths. To study distance estimation, we developed a head-fixed strike assay. We found that we could evoke strike behavior in head-fixed larvae and quantify head movements to classify the behavior as a strike. Strikes were dependent on distance to prey, allowing us to use them to study distance estimation. Light intensity is rapidly attenuated as it travels through water, so we hypothesized that larvae could use intensity as a distance cue. We found that increasing stimulus intensity could cause larvae to strike at prey that would normally be out of range, and decreasing the intensity could lower the strike rate even for very proximal stimuli. In addition, stimulus contrast is a key parameter, and this could allow larvae to estimate distance over the range of natural illumination. Finally, we presented prey in the binocular vs. monocular visual field and found that monocular prey did evoke strikes, although the binocular input produced more. These results suggest that strike behavior is optimally evoked by bright UV dots in the binocular zone with minimal UV background light and provide a foundation to study the neuronal mechanisms of distance estimation.
确定物体距离的能力是大多数视觉系统的一个重要特征，但对于距离估计的神经元机制知之甚少。幼虫斑马鱼根据距离执行不同的视觉行为；在中等距离，它们会聚眼睛并靠近，但当猎物足够近时，它们会执行一个攻击并将猎物吸入口中。为了研究距离估计，我们开发了一个头部固定的攻击测定法。我们发现，我们可以在头部固定的幼虫中引发攻击行为，并量化头部运动，将行为分类为攻击。攻击行为取决于与猎物的距离，这使我们能够使用它们来研究距离估计。光强度在水中传播时会迅速衰减，因此我们假设幼虫可以使用强度作为距离线索。我们发现，增加刺激强度可以使幼虫攻击通常超出范围的猎物，而降低强度甚至对于非常接近的刺激也会降低攻击率。此外，刺激对比度是一个关键参数，这可以使幼虫在自然光照范围内估计距离。最后，我们在双眼与单眼视觉场中呈现猎物，发现虽然单眼输入产生的更多，但单眼猎物确实会引发攻击。这些结果表明，明亮的 UV 点在双眼区域以最小的 UV 背景光最佳地引发攻击行为，并为研究距离估计的神经元机制提供了基础。
