Population receptive field analysis in subjects with area V1+ lesions.

描述（由申请人提供）：视觉功能障碍是中风和其他几种类型的皮质损伤的常见后果。后循环梗塞、出血或创伤性脑损伤通常对视觉皮质网络（包括初级视觉皮质）造成不同程度的损伤，导致部分或完全同向性偏视或斜视。临床上最常见的视觉皮质损伤涉及初级视觉皮质（V1）。V1是视觉输入到更高（纹状外）皮质区域的主要中继，V1病变导致对侧致密暗斑，其中视觉严重受损。由此产生的视力缺陷长期以来被认为是难以康复的，即基本上是不可逆转的。然而，希望可能不会完全消失。在精心控制的条件下，人类和猴子的V1病变引起的暗斑中，处理视觉属性（如运动）的有限能力通常持续存在（“盲视”）。盲视性能随着训练的提高而提高（Weiskrantz L, Prog Brain Res, 44:229- 41,2004; Huxlin et ., J Neurosci. 29(13):3981- 91,2009）提出了希望，更好的康复策略可能有一天能够增加V1旁路通路的强度，以部分补偿V1输入的损失。然而，视力康复仍然具有挑战性，个体患者的视力康复能力变化很大（图3）。了解哪些区域的视野更适合康复，并研究潜在的康复机制是很重要的。功能磁共振成像（fMRI）可用于绘制正常视觉皮层的群体感受野（pRF）特性（Dumoulin等人，J Neurosci, 2008）。这提供了一个独特的机会来详细描述，逐体素，在V1+区域损伤后，幸免视觉区域的prf是如何组织的。然而，为了做到这一点，必须改进pRF映射方法，以消除在感知暗点边界附近的pRF估计中出现的偏差（图1,5,6）。我们将研究V1+病变导致的慢性偏视和象限视患者队列和年龄匹配的对照。具体目标#1将开发一种估算pRF地形的直接方法，这种方法不容易产生偏差（图1、5、6）。具体目标#2将描述与对照组相比，患有慢性V1+病变的受试者的视野表征和备用视觉区域的pRF特性有何不同。从感知暗点内的视野位置调制的空闲视觉区域的能力将确定更适合康复的位置。具体目标#3将测试视觉运动知觉的康复训练通过增加运动选择复合体（hV5/MT+）对视觉运动刺激的敏感性来提高表现的假设。这种效果在训练前可以视觉调节hV5/MT+区域的暗斑区域尤其强烈（SA #2）。总的来说，我们的方法将描述下游区域如何适应慢性V1+损伤，并将为指导未来的康复训练提供新的方法。

DESCRIPTION (provided by applicant): Visual malfunction is a common corollary of stroke and several other types of cortical injury. Posterior circulation infarcts, hemorrhages or traumati brain injury often produce varying degrees of damage to visual cortical networks, including the primary visual cortex, resulting in partial or complete homonymous hemianopias or quadrantanopias. The most common clinically significant visual cortical injury involves the primary visual cortex (V1). V1 is the chief relay of visual input to higher (extra striate) cortica areas and V1 lesions result in a dense contralateral scotoma within which visual perception is severely impaired. The resulting visual deficit is long thought to be highly resistant to rehabilitation, i.e. essentially irreversible. Hope, however, may not be entirely lost. Under carefully controlled conditions a limited capacity to process visual attributes such as motion often persists inside scotomas induced by V1 lesions, both in humans and monkeys ("blindsight"). Blindsight performance improves with training (Weiskrantz L, Prog Brain Res, 144:229-41, 2004; Huxlin et al., J Neurosci. 29(13):3981-91, 2009) raising the hope that better rehabilitation strategies may one day be able to increase the strength of V1-bypassing pathways to partially compensate for the loss of V1 input. Visual rehabilitation however remains challenging and the capacity of individual patients for visual rehabilitation highly variable (fig.3). It is important to understand which areas of the visual field are more amenable to rehabilitation and to study possible mechanisms underlying recovery. Functional magnetic resonance imaging (fMRI) can be used to map population receptive field (pRF) properties in normal visual cortex (Dumoulin et al., J Neurosci, 2008). This offers a unique opportunity to characterize in detail, voxel by voxel, how pRFs in spared visual areas are organized following area V1+ injuries. However, in order to do so, the pRF mapping methodology has to be refined to eliminate biases that occur in pRF estimation near the border of a perceptual scotoma (fig. 1, 5, 6). We will study a patient cohort with chronic hemianopia and quadrantanopia as a result of V1+ lesions and age-matched controls. Specific aim #1 will develop a direct method of estimating pRF topography that is less prone to bias (figs 1, 5, 6). Specific aim #2 will characterize how visual field representation and pRF properties in spared visual areas differ in subjects with chronic V1+ lesions compared to controls. The capacity of spared visual areas to be modulated from visual field locations within the perceptual scotoma will identify locations more amenable to rehabilitation. Specific aim #3 will test the hypothesis that rehabilitative training in visual moton perception improves performance by increasing the sensitivity of the motion selective complex (hV5/MT+) to visual motion stimuli. This effect will be particularly strong in regions of the scotoma that can visually modulate area hV5/MT+ before training (SA #2). Overall, our approach will characterize how downstream areas adjust to chronic V1+ injury, and will suggest new ways to guide rehabilitative training in the future.