Adaptive Neuroplasticity Following Central Visual Field Loss in Macular Degeneration

摘要 黄斑变性（MD）是一种视网膜疾病，在全球近700万人中导致严重的视力障碍。 这种疾病导致视网膜中心的光感受器进行性退化， 与黄斑一样，并使患者无法看到视野中心。因此，患者 患有MD的人必须依赖周边视觉，即使是最简单的日常任务，如阅读或 识别人脸要困难得多依赖周边视觉是非常有问题的，因为它具有 与中央视觉相比，分辨率低得多。事实上，许多患者从未完全适应使用 周边视觉有效。然而，有趣的是，一些患者变得特别熟练地使用他们的 保留了周边视觉先前的研究表明，这种使用周边视觉的适应发生在一个特定的时间点。 在视网膜以外的处理阶段，特别是在视觉皮层。文献中有关于 以前对中央（丧失）视觉作出反应的大脑区域是否重新映射了它们的功能， 周边（备用）视觉。我们在这里讨论一种不同形式的可塑性：大脑区域的重塑 最初对周边（备用）视觉做出反应，以便他们更有能力承担 中央视觉的功能。我们的假设是，周边视觉皮层建立新的 这改变了该区域的结构和功能。使用神经成像 （磁共振成像）在人类参与者中，我们已经产生了初步证据，表明 这些变化中的一些可能以改变大脑结构的形式存在（神经突密度和皮质 厚度）和大脑功能（功能连接）。例如，我们已经观察到， 与健康人相比，MD患者对周边视觉有反应的皮质厚度更大 控制，这表明可能的补偿机制，可能与加强使用 周边视觉此外，我们还观察到MD患者早期视皮层的周边区域， 更强的功能连接到后来的视觉区域，选择性地响应特定类型的视觉， 刺激，如面部特征和单词/字母。我们将检验一个假设，即更好地使用外围设备 MD患者的视力与增强的功能连接和增强的结构（神经突）有关 密度和皮质厚度）。更具体地说，我们预测，增强视觉功能的MD将是 与初级视觉皮层和后期视觉皮层的外围区域之间更强的功能连接有关 优先响应刺激类别的区域（即-脸和话语）。此外，我们预测， 初级视皮层神经突密度和皮层厚度越大，则与行为表现相关 视觉处理任务。这些发现将有助于为改善治疗干预提供见解 以及揭示有关成人大脑适应经验变化的潜力的知识。

ABSTRACT Macular degeneration (MD) is retinal disease that causes severe visual impairment in nearly 7 million people in the U.S. This disease causes the progressive deterioration of photoreceptors in the center of the retina, known as the macula, and renders patients unable to see in the center of the visual field. As a consequence, patients with MD must rely on peripheral vision, making even the simplest everyday tasks, such as reading or recognizing faces, much more difficult. Reliance on peripheral vision is extremely problematic, as it possesses substantially lower resolution compared to central vision. In fact, many patients never fully adapt to using peripheral vision effectively. Interestingly, however, some patients become particularly skilled at using their spared peripheral vision. Prior work suggests that this adaptation to using peripheral vision happens at a processing stage beyond the retina, specifically in visual cortex. There is debate in the literature about whether or not brain regions that formerly responded to central (lost) vision remap their function to respond to peripheral (spared) vision. We address a different form of plasticity here: remodeling of the brain regions which originally responded to peripheral (spared) vision so that they are more capable of taking on the functions of central vision. Our hypothesis is that peripherally-representing visual cortex builds new connections after experience, and this changes the structure and function of that region. Using neuroimaging (Magnetic Resonance Imaging) in human participants, we have generated preliminary evidence that suggests that some of these changes may exist in the form of alterations to brain structure (neurite density and cortical thickness) and brain function (functional connectivity). For example, we have observed that the parts of visual cortex that respond to peripheral vision have greater cortical thickness in MD patients compared to healthy controls, suggesting a possible compensatory mechanism that may be associated with enhanced use of peripheral vision. Additionally, we have observed that peripheral regions of early visual cortex in MD patients are more strongly functionally connected to later visual areas that selectively respond to specific types of visual stimuli, such as facial features and words/letters. We will test the hypothesis that better use of peripheral vision in MD is associated with enhanced functional connectivity and enhanced structure (neurite density and cortical thickness). More specifically, we predict that enhanced visual function in MD will be related to stronger functional connectivity between peripheral areas of primary visual cortex and later visual areas that respond preferentially to categories of stimuli (i.e.- faces, and words). Additionally, we predict that greater neurite density and cortical thickness in primary visual cortex will be related to behavioral performance on visual processing tasks. These findings will help provide insight towards improving therapeutic interventions for MD, as well as uncover knowledge about the adult brain’s potential for adaptation to changes in experience.