Properties of training-induced visual recovery in cortical blindness

 描述(申请人提供)：皮质性失明(CB)是由初级视觉皮质受损引起的，表现为对侧视野的视力丧失。我的实验室和其他实验室的工作之前已经表明，视觉训练可以在CB受试者受过训练的盲区位置恢复简单和复杂的视觉运动辨别。然而，恢复的对比敏感度和对细微方向差异的辨别能力比 视野的完整部分，表明恢复的视力并不完全功能。这项拨款的主要问题是：在学习的特征处理和空间迁移方面，这些残留的视觉缺陷能否在CB视野中克服？为了解决这个问题，我开发了两个具体的目标来测试(1)操纵基于特征的注意(FBA)或空间注意(SA)是否有助于克服残留的视觉缺陷，以及(2)训练诱导的恢复位置是否可以通过备用视网膜活动区域来预测。在第一个目标中，我将调查在进行粗略方向辨别的心理物理训练后，仍然无法进行精细方向辨别的情况。我将尝试使用FBA和SA结合视觉辨别训练来克服这种损害，以恢复视觉表现。FBA和SA在视觉完好的受试者中都被证明可以促进精细辨别阈值的提高，它们在CB受试者中可能也会有同样的效果。我的第二个目标是研究CB受试者的视野与视网膜视功能之间的关系。训练诱导的恢复在视网膜定位上局限于相对于盲区深度的训练位置，而不是沿着盲场边界。我将检验这样一种假设，即恢复的位置可以基于预训练来预测 功能磁共振成像视网膜定位图，这种视觉只能在存在残留皮质活动的视野区域恢复。Humphrey视野检查以及方向和方位辨别的心理物理测量将被用来评估训练诱导的恢复的空间程度，这将与从功能磁共振成像获得的视网膜定位图相关联。最后，我将评估是否以及在多大程度上可以通过操纵外源性空间注意来克服盲视视野深处恢复的视网膜特异性。这些实验将进一步揭示训练诱导的视觉恢复在大脑皮层盲区的特性，记录注意操作对训练的影响，研究训练诱导恢复的可能机制，并确定恢复的视觉的空间扩散和局限性。更好地了解这些特性不仅将有助于治疗皮质盲，而且还将通过研究大型永久性损伤后视觉功能恢复的程度来提高我们对视觉系统中可塑性的理解。

 DESCRIPTION (provided by applicant): Cortical blindness (CB) results from damage to the primary visual cortex, presenting as a loss of vision in the contralateral visual field. Work from my lab and others have previously shown that visual training can recover simple and complex visual motion discriminations at trained, blind field locations in CB subjects. However, recovered contrast sensitivity and discrimination of fine direction differences are poor compared to those in intact portions of the visual field, suggesting that recovered vision is not fully functional. The main question addressed in this grant is: can these residual visual deficits be overcome in CB fields, both with respect to feature processing and spatial transfer of learning? To address this question, I have developed two specific aims to test (1) whether manipulating feature-based attention (FBA) or spatial attention (SA) will aid in overcoming residual visual deficits and (2) whether locations of training induced recovery are predicted by regions of spared retinotopic activity. In the first aim I will investigate the residual inability to perform fine direction discriminations following psychophysical training on coarse direction discrimination. I will attempt to overcome this impairment using FBA and SA coupled with visual discrimination training to recover visual performance. Both FBA and SA have been demonstrated in visual intact subjects to promote improvement of fine discrimination thresholds, and they will likely have the same effect in CB subjects. My second aim investigates the relationship between the visual field of CB subjects and retinotopic activity. Training-induced recovery is retinotopically localized to trained locations with respect to depth in the blind field, but not along the blind fild border. I will test the hypothesis that location of recovery can be predicted based on pre-training fMRI retinotopic maps and that vision can be recovered only in regions of the visual field where residual cortical activity is present. Humphrey perimetry and psychophysical measures of direction and orientation discrimination will be used to assess the spatial extent of training-induced recovery, which will be correlated with retinotopic maps obtained from fMRI. Finally, I will assess whether and to what extent retinotopic specificity of recovery deep into the blind fiel can be overcome by manipulating exogenous spatial attention. The proposed experiments will provide further insights into the properties of training-induced visual recovery in cortically blin fields, documenting the effects of attentional manipulations on training, investigating a possible mechanism by which training induced recovery occurs, and determining the spatial spread and limitations of recovered vision. A better understanding of these properties will not only improve treatment cortical blindness, but will also improve our understanding of plasticity within the adul visual system by studying to what extent visual function can recover following a large, permanent injury.