Individual Differences in Color Vision Assessed with Chromatic Textures

患有轻度创伤性脑损伤的退伍军人经常报告视力问题，尽管正常或接近正常 临床视觉传入检查的表现。令人惊讶的是，在听觉领域也观察到了类似的模式， 这提出了两种可能重叠的解释，解释了mTBI的(多)感觉缺陷：(A)损害 上升的感觉通路产生微妙的缺陷，这在标准的临床测试中可能是无法检测到的； 以及(B)感觉处理或认知、情感或联想大脑的更中枢水平的变化 网络导致在处理复杂感觉环境方面的缺陷。因此，理想的感官测量 MTBI中的容量应考虑到这些不同处理级别的变化。回到……的领域 视觉，最近的研究表明，颜色视觉对后天获得性疾病或创伤高度敏感， 早期视觉通路。同时，颜色在物体等高级视觉功能中扮演着重要的角色 种族隔离和视觉注意。这些特性使色觉成为评估视觉的理想候选者 在mTBI中的功能。然而，目前的色觉测试主要集中在检测(主要是先天性的)损失 起源于视网膜颜色感受器。这项拟议的研究开始开发一种新的色觉测试 旨在捕捉视觉处理的低(例如，视网膜)和高(例如，皮质)水平的变化。这个测试 依赖于对其单个元素被指定为等亮度阴影的彩色纹理的辨别 沿着从纯绿色到纯红色的连续体。颜色的分布遵循统计模式，使得 区分具有相反图案的两种纹理依赖于视觉系统提取这些纹理的能力 模式。不同类型的图案被用来探索色彩处理的不同方面。模式提取是 假设依赖于对不同深浅的红色和/或绿色以及 ‘混合模块’，允许以不同的方式组合这些机制，以编码不同的模式。一个 使用纹理辨别性能的数学模型来列举一组观察者：(A) 低级别机制的数量和结构；(B)每个观察员对这些机制的敏感性；以及 (C)每个观察者的独特混合比例。采用不同色度纹理图案的性能 以反映特定观察者对红绿视觉的独特轮廓。本提案旨在验证这一范例在 年龄较小的群体(25-34岁)年龄更大(55岁-)具有正常色觉的退伍军人，考虑到低级别的颜色 已知敏感度每十年下降约10%，高水平的个体差异很大 年龄段内和年龄段之间的色彩处理。第一个具体目标是确定色度是否 纹理识别捕捉到了色彩处理的各个方面，而不是成熟的色度所捕捉的那些 敏感度测量。颜色评估和诊断中的红绿色敏感度阈值 (CAD)测试将以因子分析模型中的彩色纹理辨别阈值进入，其中 假设彩色纹理辨别阈值将加载不同于CAD阈值的因素。 一种新的基于颜色定义的相干运动的色敏感度阈值上的度量将是 包括以捕捉较高处理级别的颜色敏感度的变化。第二个具体目标 将应用前面提到的彩色纹理辨别的数学模型来表征个体 自下而上(机构敏感度)和自上而下(机构混合)颜色处理的差异。 这些目标的实现将使颜色视觉测试--基于纹理或其他--的部署 通过提供多个色觉正常变化的基线来表征mTBI的视觉缺陷 年龄和加工水平。值得注意的是，红色-绿色纹理辨别范例可以很容易地扩展到 黄蓝色和灰度级视觉。这项工作的长期目标是将基于纹理的和其他 复杂视觉功能测试和相关的复杂听觉功能测试，以确定程度 不同加工水平的多感觉缺陷导致了mTBI中观察到的功能缺陷。

Veterans with mild traumatic brain injury (mTBI) often report visual problems despite normal or near-normal performance on clinical tests of afferent vision. Strikingly, a similar pattern is observed in the auditory domain, which suggests two potentially overlapping explanations for the (multi-)sensory deficits in mTBI: (a) damage to the ascending sensory pathways produces subtle deficits that may not be detectable on standard clinical tests; and (b) changes at more central levels of sensory processing or in cognitive, affective, or associative brain networks lead to deficits in processing complex sensory environments. Therefore, an ideal measure of sensory capacity in mTBI should account for changes at these different levels of processing. Returning to the domain of vision, recent research suggests that color vision is highly sensitive to acquired disorders or trauma affecting the early visual pathway. At the same time, color plays a significant role in higher visual functions such as object segregation and visual attention. These properties make color vision an ideal candidate for assessment of visual function in mTBI. However, current tests of color vision focus on detection of (primarily congenital) losses originating at the retinal color receptors. The proposed study begins to develop a new test of color vision designed to capture changes at low (e.g., retinal) and high (e.g., cortical) levels of visual processing. The test relies on discrimination of chromatic textures whose individual elements are assigned an equiluminant shade along a continuum from pure green to pure red. The distribution of colors follows a statistical pattern such that discrimination among two textures with opposing patterns relies on the visual system’s ability to extract those patterns. Different types of patterns are used to probe different aspects of color processing. Pattern extraction is assumed to rely on a limited number of mechanisms sensitive to different shades of red and/or green and a ‘mixing module’ that allows the mechanisms to be combined in different ways to encode different patterns. A mathematical model of texture discrimination performance is used to enumerate, for a group of observers: (a) the number and structure of the low-level mechanisms; (b) each observer’s sensitivity to those mechanisms; and (c) each observer’s unique mixing proportions. Performance across different chromatic texture patterns is taken to reflect a given observer’s unique profile of red-green vision. This proposal aims to validate this paradigm in groups of younger (25-34 yrs.) and older (55-64 yrs.) Veterans with normal color vision, given that low-level color sensitivity is known to decrease by ~10% per decade of life with considerable individual differences in high-level color processing within and between age groups. The first specific aim is to determine whether chromatic texture discrimination captures aspects of color processing beyond those captured by well-established chromatic sensitivity measurements. Red-green chromatic sensitivity thresholds from the Color Assessment and Diagnosis (CAD) test will be entered with chromatic texture discrimination thresholds in a factor analytic model, where the hypothesis is that chromatic texture discrimination thresholds will load on a different factor than CAD thresholds. A novel ‘suprathreshold’ measure of chromatic sensitivity based on color-defined coherent motion will be included to capture variation in chromatic sensitivity at higher levels of processing. The second specific aim will apply the aforementioned mathematical model of chromatic texture discrimination to characterize individual differences in bottom-up (mechanism sensitivity) and top-down (mechanism mixing) color processing. Achievement of these aims will allow deployment of color vision tests – texture-based or otherwise – to characterize the visual deficits in mTBI by providing a baseline for normal variation in color vision at multiple ages and levels of processing. Notably, the red-green texture discrimination paradigm can be easily extended to yellow-blue and grayscale vision. The long-term goal for this line of work is to combine texture-based and other tests of complex visual function with related tests of complex auditory function to determine the extent to which multisensory deficits at different levels of processing contribute to the functional deficits observed in mTBI.