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Exploring the neural machinery of color vision: A bold fMRI-based investigation.

机译：探索彩色视觉的神经机制：基于fMRI的大胆研究。

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摘要

The chromatic content of the environment acts as a powerful sensory cue to our visual system. Perceptually, we are intimately aware of associations that can be made based on chromatic variation within the visual scene. For instance, spotting a piece of ripe fruit amongst dappled foliage (or amongst other fruit at the market) is relatively trivial, yet intuitively quite powerful. The roles of chromatic cues in other aspects of vision are less intuitive but presumably still very important in guiding behavior. Chromatic signals are linked to circadian circuitry and it has long been appreciated that chromatic information can be used in the processing of motionbased visual stimuli. These are two examples of how chromatic information can be used for visual functions that are distinct from hue perception. The focus of this dissertation is chromatic signal processing in the retina and brain. Our hope is to show that understanding the many roles of chromatic signals is important, and by exploring these roles we can obtain a better understanding of color vision.;The short-wavelength sensitive (S-) cone photoreceptor generates a signal that is critically important for encoding chromatic information and there is evidence that neural circuit features associated with the S-cone are conserved across mammalian species. At the heart of this proposal is a straightforward circuit model, wherein, the following has classically been proposed: at the level of the retina, Scone signals are conveyed exclusively by metabotropic glutamate signaling (mGluR6) from S-cones to S-cone specific bipolar cells. Thus it follows that all centrally projected S-cone signals must traverse the mGluR6 mechanism. We tested the foregoing circuit model in humans (genetics) and animals (pharmacology) using blood oxygenation dependent functional magnetic resonance imaging (BOLD fMRI). BOLD fMRI is a powerful neuroimaging technique that allows whole brain function to be assessed at different temporal and spatial scales. This allowed us to not only test the current circuit model but also infer the role(s) of S-cone signals by evaluating the response properties of different brain areas across species.;We used the well-known mGluR6 agonist 2-amino-4-phosphonobutanoic acid to selectively block the putative pathway in animals. In humans, we studied patients with genetic mutations that render the mGluR6 signaling pathway nonfunctional. We presented diffuse stimuli that were chromatically modulated to stimulate only S-cones. In both 'lesion' models S-cone signals should have been absent from all downstream pathways. In each model studied S-cone responses were selectively attenuated, but not for all visual areas and/or experimental conditions. In animals, selective attenuation was observed in subcortical structures implicated in circadic functions: the olivary pretectal nucleus, pretectal area, pregeniculate, and ventral lateral geniculate nucleus. In human patients, dorsal stream visual areas were less responsive to S-cone stimuli modulated at high temporal frequencies. The attenuation of S-cone signals in both models is consistent with the mGluR6 theory and is further supported by central projections of 'S-cone carrying' ganglion cells. However, in all models tested we observed persistent Scone signals in the primary retinogeniculostriate pathways. These findings allow us to reject the current circuit model. That is, in addition to the mGluR6 mechanism, there must be an alternative mechanism-pathway that makes a major, if not sole contribution to the retinogeniculatestriate pathway. One potential candidate is the direct feed-forward GABAergic signaling from H2 horizontal cells. This pathway may be the primary source of S-cone signals supporting hue percepts.
机译：环境中的彩色内容为我们的视觉系统提供了强大的感官提示。从视觉上讲，我们非常了解可以根据视觉场景中的色度变化进行的关联。例如，在斑驳的叶子（或市场上的其他水果）中发现一块成熟的水果是相对琐碎的，但直观上却很强大。色彩提示在视觉其他方面的作用虽然不那么直观，但在引导行为方面仍然很重要。色度信号链接到生物钟电路，人们早已认识到，色度信息可以用于基于运动的视觉刺激的处理。这是如何将色度信息用于与色觉不同的视觉功能的两个示例。本文的重点是视网膜和大脑中的彩色信号处理。我们的希望是表明了解彩色信号的许多作用很重要，并且通过探索这些作用，我们可以更好地了解彩色视觉。;短波敏感（S-）锥型感光体产生的信号至关重要用于编码色度信息的证据，并且有证据表明与S-锥体相关的神经回路特征在整个哺乳动物物种中都得到了保留。该提议的核心是一个简单的电路模型，其中经典地提出了以下模型：在视网膜水平上，斯康信号仅通过代谢型谷氨酸信号（mGluR6）从S锥传递到S锥特定的双极。细胞。因此，所有集中投影的S锥信号必须经过mGluR6机制。我们使用依赖于血液氧合的功能磁共振成像（BOLD fMRI）在人（遗传学）和动物（药理学）中测试了上述电路模型。粗体功能磁共振成像是一种强大的神经影像技术，可以在不同的时空尺度上评估整个大脑的功能。这不仅使我们能够测试当前的电路模型，还可以通过评估物种间不同大脑区域的响应特性来推断S-圆锥信号的作用。;我们使用了著名的mGluR6激动剂2-amino-4 -膦酰基丁酸选择性地阻断动物的推定途径。在人类中，我们研究了具有导致mGluR6信号通路无功能的基因突变的患者。我们提出了经色调制以仅刺激S锥的弥散刺激。在两个“病变”模型中，所有下游途径均应缺少S-cone信号。在每个研究的模型中，S-圆锥体响应均被选择性减弱，但并非在所有视觉区域和/或实验条件下均被减弱。在动物中，在涉及皮下功能的皮质下结构中观察到选择性衰减：橄榄形的前盖状核，前盖区，前膝状体和腹侧膝状膝状体核。在人类患者中，背流视觉区域对在高时间频率上调制的S-圆锥刺激反应较慢。两种模型中S-cone信号的衰减均与mGluR6理论一致，并进一步受到“带有S-cone的”神经节细胞中心投影的支持。但是，在所有测试的模型中，我们都观察到了主要的维甲酸原糖途径中的持续Scone信号。这些发现使我们可以拒绝当前的电路模型。也就是说，除了mGluR6机制外，还必须有一种替代性的机制途径，即使不是唯一的途径，也可能对视黄醛-视网膜纹状体途径产生重大影响。一种潜在的候选物是来自H2水平细胞的直接前馈GABA能信号。该途径可能是支持色调感知的S-圆锥信号的主要来源。

著录项

  • 作者

    Salzwedel, Andrew P.;

  • 作者单位

    The Medical College of Wisconsin.;

  • 授予单位 The Medical College of Wisconsin.;
  • 学科 Biology Neuroscience.;Biology General.;Biophysics Biomechanics.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 157 p.
  • 总页数 157
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 高分子化学（高聚物）;
  • 关键词

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