The neural basis of color vision: (I) photoreceptor interactions and origin of color opponent processing.

色觉的神经基础：（I）感光器相互作用和颜色对手处理的起源。

• 批准号: 408330929
• 负责人: Professor Dr. Dierk F. Reiff
• 金额: --
• 依托单位: Abteilung Neuro- und Verhaltensbiologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/408330929?language=en
• 关键词: neural; basis; color; vision; photoreceptor

Color vision is an important sensory capability that enables many animals to differentiate spectral content independent of intensity. It provides animals with additional power for the detection of objects and interactions with the environment. Most of our knowledge on its neural basis comes from vertebrate research, in particular on the retina, where many of the underlying neuronal circuits, cell types, synaptic interactions, and processing mechanisms have been revealed. We know that signals of photoreceptors with different spectral sensitivities are combined antagonistically by the nervous system, employing a mechanism akin subtraction. Humans and other trichromatic primates for instance combine short (S), middle (M) and long (L) wavelength sensitive cone photoreceptors to create L–M and S–(L+M) color opponent pathways. This color-opponent processing overcomes the shortcoming of photoreceptors that inherently confound wavelength and intensity and enables the detection and enhancement of spectral contrast. Little is known about the neural basis of color vision in none-vertebrates. Combined behavioral and computational studies suggest that color-opponent processing is implemented in the nervous system of Drosophila (and likely ‘all’ animals with color vision). However, physiological recordings from cells of the color detection system in Drosophila have not been feasible so far. ln our recent study we overcame this major roadblock and we recorded the signals of ~3500 photoreceptors in about 40 different genotypes. Contradicting the common thought in the field, our recordings showed that color-opponency is already implemented in the terminals of inner photoreceptors R7/R8 in the medulla. We revealed detailed insights into the underlying synaptic pale- and yellow-specific circuit mechanisms and we deduced a simplified circuit model that now allows us to predicting ‘missing’ processing steps. Based on these predictions and our technical achievements I am here presenting a comprehensive research plan to reveal the immediate next processing mechanisms, in particular the neural basis of spectral feedback inhibition of R7p/y and R8p/y, respectively. We will reach this goal by applying a combined genetic, anatomical, and physiological approach that represents the state-of-the-art in the field. We will characterize the receptive field properties of identified neurons with an emphasis on their chromatic and spatiotemporal organization. Finally, we will use the obtained information to extend our model and to identify novel candidate neurons of the color vision system in Drosophila. By this work we will contribute to a better understanding of color vision in the ecologically important group of insects and we will provide insights into the variability of the circuit implementation of color vision across taxa.

色觉是一种重要的感觉能力，使许多动物能够区分光谱内容，而不依赖于强度。它为动物提供了额外的力量来检测物体和与环境的相互作用。我们对它的神经基础的大部分知识来自脊椎动物的研究，特别是对视网膜的研究，其中许多潜在的神经元回路，细胞类型，突触相互作用和处理机制已经被揭示。我们知道，具有不同光谱灵敏度的光感受器的信号通过神经系统进行拮抗性组合，采用类似减法的机制。例如，人类和其他三色灵长类动物将短（S）、中（M）和长（L）波长敏感的视锥光感受器联合收割机组合起来，以创建L-M和S-（L+M）颜色对手路径。这种颜色对手处理克服了感光器固有地混淆波长和强度的缺点，并且使得能够检测和增强光谱对比度。关于非脊椎动物的色觉的神经基础知之甚少。结合行为和计算的研究表明，颜色对手的处理是在果蝇的神经系统中实现的（可能是“所有”具有色觉的动物）。然而，生理记录细胞的颜色检测系统在果蝇还没有可行的。在我们最近的研究中，我们克服了这个主要障碍，我们记录了大约40种不同基因型的~3500种光感受器的信号。与该领域的普遍想法相矛盾，我们的记录表明，在延髓的内部光感受器R7/R8的末端中已经实现了颜色可变性。我们揭示了潜在的突触苍白和黄色特定的电路机制的详细见解，我们推导出一个简化的电路模型，现在允许我们预测“丢失”的处理步骤。基于这些预测和我们的技术成就，我在这里提出了一个全面的研究计划，以揭示下一个加工机制，特别是光谱反馈抑制的R7 p/y和R8 p/y，分别的神经基础。我们将通过应用代表该领域最先进技术的遗传学、解剖学和生理学相结合的方法来实现这一目标。我们将确定神经元的感受野特性的特点，强调其色彩和时空组织。最后，我们将使用所获得的信息来扩展我们的模型，并确定新的候选神经元的颜色视觉系统在果蝇。通过这项工作，我们将有助于更好地了解生态上重要的昆虫群体的色觉，我们将提供见解的变化，电路实现色觉跨类群。