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，在中国近700万人中导致严重的视力障碍 美国的这种疾病会导致视网膜中央感光细胞的进行性退化，众所周知 作为黄斑，并使患者在视野中央看不见。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，因为它拥有 与中心视觉相比，分辨率大大降低。事实上，许多患者从未完全适应使用 有效的周边视力。然而，有趣的是，一些患者变得特别擅长使用他们的 保留了周边视力。先前的工作表明，这种对使用外围视觉的适应发生在 视网膜以外的加工阶段，特别是在视觉皮质。在文学作品中有关于 以前对中枢(丧失)视力作出反应的大脑区域是否重新映射其功能以作出反应 周边(保留)视力。我们在这里讨论了一种不同形式的可塑性：大脑区域的重塑 最初对外围(备用)视觉做出反应，以便他们更有能力承担 中心视觉的功能。我们的假设是，代表外周的视觉皮质建立了新的 经历之后的联系，这改变了那个区域的结构和功能。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 其中一些变化可能以大脑结构(轴突密度和皮质)的改变的形式存在 厚度)和脑功能(功能连接)。例如，我们观察到视觉的部分 与健康人相比，MD患者对周边视觉有反应的皮质厚度更大 提出了一种可能的补偿机制，这可能与加强使用 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 在功能上更强地连接到后来的视觉区域，这些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。我们将检验以下假设：更好地利用外围设备 MD的视力与增强的功能连通性和增强的结构(轴突)相关 密度和皮质厚度)。更具体地说，我们预测MD的增强视觉功能将是 与初级视觉皮质外围区域和后来的视觉区域之间更强的功能连接有关 优先对不同类别的刺激作出反应的区域(即-脸和词)。另外，我们预测， 初级视皮层中较大的轴突密度和皮质厚度将与行为表现有关 在视觉处理任务上。这些发现将有助于为改进治疗干预措施提供洞察 对于MD，以及发现关于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.