Retinotectal circuitry of larval zebrafish is adapted to detection and pursuit of prey.
Retinotectal circuitry of larval zebrafish is adapted to detection and pursuit of prey.
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DOI：
10.7554/elife.58596
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发表时间：
2020-10-12
期刊：
影响因子：
7.7
通讯作者：
Baier H
中科院分区：
文献类型：
--
作者：
Förster D;Helmbrecht TO;Mearns DS;Jordan L;Mokayes N;Baier H
视网膜轴突投影形成顶盖视觉环境的地图。斑马鱼幼虫通常会在其周边视野中检测到猎物。当它转身游向猎物时，刺激物进入中央双眼区域，并且尺寸似乎扩大了。通过体积钙成像，我们发现后顶盖神经元（用于远距离检测猎物）倾向于对小物体做出反应并内在地计算它们的运动方向。前顶盖中的神经元（在捕捉攻击之前不久代表猎物图像）被调整为更大的物体尺寸，并且通常没有方向选择性，这表明主要是眼间比较用于计算近距离物体的运动。顶盖特征图源自多样化、功能专门化、层板特异性和拓扑排序的视网膜神经节细胞突触输入的线性组合。我们得出的结论是，顶盖上的局部细胞类型组成和连接性适应于位置依赖的、行为相关的物体特征的处理。视网膜是眼睛中的薄层组织，可以接收光刺激并将其转换成电信号传输到大脑。感知精细细节的细胞聚集在视网膜的中心，而跟踪运动的运动感知细胞则位于视网膜的外围。当斑马鱼幼虫捕猎时，当猎物穿过它们的周边视野时，它们的运动感应细胞就会被触发。然后他们转身游向它。当它们接近时，猎物图像移动到视网膜的细节感知部分，并且看起来更大，在近距离填充更多的视野。然后，这些信号在大脑的特定部分进行处理，特别是在称为视顶盖的区域。该区域是如何响应眼睛的组织和狩猎的要求而组织的仍不清楚。福斯特等人。着手探索斑马鱼幼虫的狩猎习惯如何影响视顶盖神经元的排列。幼虫接触到代表猎物捕获过程各个方面的不同图像：小移动点代表远处经过的猎物，而大移动点代表捕获前的猎物。测量视顶盖神经元的活动表明，就像眼睛一样，不同的区域专门负责不同的任务。顶盖的背面经常被小点激活，并确定它们在第一个狩猎步骤中移动的方向。顶盖的前部对大点反应最好，常常忽略它们的方向，并帮助幼虫直接追踪猎物。为了测试这些发现，福斯特等人。用激光摧毁了大型物体反应细胞，并观察幼虫捕食真正的猎物。没有这些细胞，鱼发现追踪和捕捉目标变得更加困难。这些结果揭示了行为与神经元在大脑中的排列方式之间的联系。未来的工作可以探索视顶盖中的不同神经元如何连接，以及它们在鱼中触发的行为。这可能有助于揭示关于感觉信息如何指导行为以及进化如何塑造大脑布局的一般原理。
Retinal axon projections form a map of the visual environment in the tectum. A zebrafish larva typically detects a prey object in its peripheral visual field. As it turns and swims towards the prey, the stimulus enters the central, binocular area, and seemingly expands in size. By volumetric calcium imaging, we show that posterior tectal neurons, which serve to detect prey at a distance, tend to respond to small objects and intrinsically compute their direction of movement. Neurons in anterior tectum, where the prey image is represented shortly before the capture strike, are tuned to larger object sizes and are frequently not direction-selective, indicating that mainly interocular comparisons serve to compute an object’s movement at close range. The tectal feature map originates from a linear combination of diverse, functionally specialized, lamina-specific, and topographically ordered retinal ganglion cell synaptic inputs. We conclude that local cell-type composition and connectivity across the tectum are adapted to the processing of location-dependent, behaviorally relevant object features. The retina is the thin layer of tissue in the eye that can receive light stimuli and convert them into electric signals to be transmitted to the brain. The cells that sense fine detail cluster at the center of the retina while the motion-sensing cells that keep track of movement lie at the periphery. When zebrafish larvae hunt, their motion-sensing cells are triggered as a prey crosses their peripheral field of view. They then turn and swim towards it. As they approach, the prey image moves to the detail-sensing part of the retina and appears larger, filling more of the field of view at close range. The signals are then processed in defined parts of the brain, in particular in a region called the optic tectum. How this area is organized in response to the organization of the eye and the requirements of the hunt is still unclear. Förster et al. set out to explore how the hunting routine of zebrafish larvae shapes the arrangement of neurons in the optic tectum. The larvae were exposed to different images representing the various aspects of the prey capture process: small moving dots represented passing prey at a distance, while large moving dots stood for prey just before capture. Measuring activity in the neurons of the optic tectum revealed that, like the eye, different areas specialize in different tasks. The back of the tectum was frequently activated by small dots and worked out which direction they were moving in during the first hunting steps. The front of the tectum responded best to large dots, often ignoring their direction, and helped the larvae to track their prey straight ahead. To test these findings, Förster et al. destroyed the large object-responsive cells with a laser and watched the larvae hunting real prey. Without the cells, the fish found it much harder to track and catch their targets. These results shed light on the link between behavior and how neurons are arranged in the brain. Future work could explore how the different neurons in the optic tectum are connected, and the behaviors they trigger in the fish. This could help to reveal general principles about how sensory information guides behavior and how evolution has shaped the layout of the brain.