The Neural Mechanism for Visual Adaptation

在脊椎动物中，杆视觉是在低光条件下以较低的视觉质量观看的能力;锥视觉在较高的光水平下起作用，并负责所有的高分辨率和彩色视觉。为了从视杆视觉过渡到视锥视觉，视网膜必须经历适应以调整神经回路的响应特性。然而，很少有人知道的神经机制，从杆锥视觉切换。本项目旨在确定视觉适应独特机制的关键神经过程。这项研究的目的是解决有关网络神经元释放特定神经递质-甘氨酸的行为如何改变视网膜回路的响应特性和光敏感性的基本问题。本研究设计了一系列实验，系统地研究了在昏暗或微光条件下锥视觉的微调过程。该项目还将使研究人员能够继续将未来科学家的研究、教育和培训融入尖端技术的重要使命，以了解神经回路的功能相互作用及其行为表现。最后，该项目将支持对当地高中和社区大学学生的推广，以及佛罗里达南部老年人的终身学习计划。 这个项目的目标是定义一个独特的机制，利用甘氨酸的网络反馈，修改中心-周围感受野组织和保护锥视觉。视锥细胞负责高分辨率视觉，但与视杆细胞相比对光不太敏感。事实上，圆锥视觉的敏感性在黄昏或黄昏时受到抑制。心理物理学研究表明，闪烁的光刺激可以提高时空敏感性（锥功能），从而提高在黄昏条件下的锥视觉。尽管有人认为这一过程与视网膜神经回路中的适应依赖性变化有关，但适应机制的细节在很大程度上是未知的。首席研究员之前的工作表明，一组网络神经元利用甘氨酸的远程反馈，可以介导视杆-视锥相互作用，从而提高暮光条件下的视锥视觉灵敏度。本项目旨在解决中心假设，即甘氨酸反馈的功能调节中心-周围感受野组织，这是锥视觉的空间和时间调谐的关键因素。主要目标是解决有关甘氨酸反馈网络的作用如何改变远端视网膜中的（i）侧抑制和（ii）突触增益和对比敏感度的基本问题。研究中将使用多种先进技术，包括电生理学、荧光成像和光刺激。这项研究的结果将扩展目前对甘氨酸仅作为抑制性神经递质发挥作用的理解，并揭示其对视网膜回路的兴奋作用。由于视网膜是中枢神经系统的一部分，与大脑共享许多神经机制，因此该提案的结果将重新定位有关甘氨酸功能的概念。此外，这些研究将为本科生和研究生提供一个独特的机会，参与并在一个高需求领域进行研究。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

In vertebrates, rod vision is the ability to see under low-light conditions with lower visual quality; cone vision functions at higher light levels and responsible for all high resolution and color vision. In order to transition from rod to cone vision, the retina must undergo adaptation to adjust the responding properties of the neural circuits. However, little is known about the neural mechanisms for switching from rod to cone vision. This project aims to identify a key neural process fundamental to the unique mechanism in visual adaptation. The objectives of the study are to address fundamental questions concerning how the actions of the network neurons releasing specific neurotransmitter - glycine, to modify the response properties and light sensitivity of the retinal circuits. A series of experiments are designed to systematically investigate this novel process involved in fine-tuning of cone vision in dim or twilight conditions. The project will also allow the researcher to continue the important mission of integrating research, education and training of future scientists in cutting-edge techniques for understanding the functional interactions of neural circuits and their behavioral manifestations. Finally, this project will support outreach to local high school, and community college students as well as the lifelong learning program for seniors in southern Florida. The goal of this project is to define a unique mechanism, utilizing network feedback of glycine, that modifies center-surround receptive field organization and subserves cone vision. Cone photoreceptors are responsible for high-resolution vision, but are less sensitive to light compared to rods. Indeed, the sensitivity of cone vision is suppressed at dusk or twilight. Psychophysical studies indicate that flickering light stimulation can improve spatial-temporal sensitivity (cone features), thereby improving cone vision in twilight conditions. Although it is argued that this process is related to adaptation- dependent changes in the retinal neural circuitry, the details of the adaptive mechanisms are largely unknown. Previous work by the principal investigator has shown that a group of network neurons, utilizing long-range feedback of glycine, can mediate rod-cone interactions that serve for improving cone visual sensitivity in twilight conditions. This project is to address the central hypothesis that the function of glycine feedback regulates the center-surround receptive field organization that is the key element for spatial and temporal tuning of cone vision. The primary objectives are to address fundamental questions concerning how the actions of glycine feedback network modify (i) the lateral inhibition and (ii) synaptic gains and contrast sensitivity in the distal retina. Multiple advanced techniques, including electrophysiology, fluorescence imaging and photic stimulation will be used in the study. The results from the study will extend the current understanding of glycine functioning solely as an inhibitory neurotransmitter and shed light on its excitatory actions on retinal circuits. As the retina is a part of the CNS and shares many neural mechanisms with the brain, the results from this proposal will reorient concepts about the function of glycine. In addition, the studies will provide a unique opportunity for undergraduate and graduate students to participate and conduct research in a high-demand area.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.