The Effects of Visual Deprivation

描述（由申请人提供）：最近发展的一种外科手术，角膜缘干细胞置换，现在允许许多以前不适合手术的患者进行角膜置换。这些患者中的许多人长期遭受视觉剥夺，因此提供了一个极其难得的机会来检查视觉功能是如何依赖于经验的。我们将研究：(1)剥夺性视力丧失的神经部位。我们将利用功能磁共振成像（fMRI）测量的心理物理（外部）对比灵敏度函数、干涉对比灵敏度函数和外侧膝状核、纹状体和纹状体外视觉区域内的神经反应功能，将基于剥夺的分辨率损失的部位划分为光学、外侧膝状核、初级和次级视觉区域。(2)作为剥夺函数的行为损失。初步数据表明，长期的视觉剥夺也会导致高级视觉过程的缺陷，比如对形状、物体和面孔的处理。相比之下，颜色和运动处理似乎相对不受长时间剥夺的影响。我们将对病人进行广泛的行为任务测试，看看剥夺的影响是如何与任务相互作用的。(3)行为丧失的神经部位。我们将根据解剖学和功能标准定义广泛的皮质视觉区域，包括外侧胫状核、V1-V4区域、运动区域MT+和被认为负责面部和物体处理的舌梭状回区域。我们将比较患者的行为表现与这些视觉区域的大小和敏感性。除了是一个独特的机会来研究剥夺对人类视觉系统的影响，这项研究应该为那些正在接受视力恢复手术的患者提供信息，告诉他们术后应该期待什么样的视力。干细胞替代是一项越来越普遍的主要手术，而其他视力恢复技术，如视网膜假体，近年来也取得了显著进展。重要的是，在选择进行视力恢复手术时，给患者一个准确的风险和收益估计。

DESCRIPTION (provided by applicant): A recently developed surgical procedure, limbal stem cell replacement, now permits corneal replacement in many patients who were previously ineligible for surgery. Many of these patients have suffered long-term visual deprivation, thus providing an extremely rare opportunity to examine how visual function is dependent on experience. We will study: (1) The neural site of deprivation-based acuity loss. We will partition the sites of deprivation-based resolution loss between the optics, lateral geniculate nucleus, and primary and secondary visual areas, using a conjunction of the psychophysical (external) contrast sensitivity function, the interferometric contrast sensitivity function and the neural response function within the lateral geniculate nucleus, striate, and extrastriate visual areas measured using functional magnetic resonance imaging (fMRI). (2) Behavioral losses as a function of deprivation. Preliminary data suggests that long-term visual deprivation also results in deficits in higher-level visual processes, such as the processing of configural form, objects, and faces. In contrast, color and motion processing seems relatively unaffected by long periods of deprivation. We will test our patients on a wide range of behavioral tasks to see how the effects of deprivation interact with task. (3) The neural site of behavioral losses. We will define, based on both anatomical and functional criteria, a wide range of cortical visual areas, including the lateral geniculate nucleus, areas V1-V4, motion area MT+ and regions in the fusiform lingual gyd thought to be responsible for face and object processing. We will compare patients' behavioral performance to the size and sensitivity of these visual areas. Besides being a unique opportunity to study the effects of deprivation on the human visual system, this research should provide patients who are undergoing sight recovery procedures with information as to what sort of sight they should expect postoperatively. Stem cell replacement is a major operation that is becoming more and more common, and other techniques for sight restoration, such as retinal prostheses, have shown remarkable progress in recent years. It is important that patients are given an accurate estimation of risks and benefits when being given the option of undergoing sight-recovery procedures.