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皮质损伤的常见推论。后循环梗塞、出血或创伤性脑损伤常对包括初级视皮层在内的视皮层网络造成不同程度的损害，导致部分或完全同义偏盲或象限失明。最常见的临床显著视皮层损伤累及初级视皮层(V1)。V1是视觉输入到较高(纹状)皮质区域的主要中继者，V1病变导致致密的对侧暗点，其中视觉感觉严重受损。长期以来，人们一直认为由此产生的视力缺陷对康复具有高度抵抗力，即基本上是不可逆转的。然而，希望可能不会完全丧失。在严格控制的条件下，在人类和猴子的V1损伤引起的暗点内，处理运动等视觉属性的有限能力经常持续存在(“盲视”)。盲人表现随着训练的提高而提高(魏斯克兰茨·L，Prog Brain Res，144：229-41,2004；Huxlin等，J Neurosci)。29(13)：3981-91,2009)带来了希望，即更好的康复策略有朝一日可能能够增加V1旁路的强度，以部分补偿V1输入的损失。然而，视力康复仍然具有挑战性，个别患者的视力康复能力存在很大差异(图3)。重要的是要了解视野的哪些区域更适合康复，并研究潜在的康复机制。功能磁共振成像(FMRI)可用于定位正常视觉皮质的群体感受野(PRF)特性(Dumoulin等人，J Neurosci，2008)。这提供了一个独特的机会来详细地描述在V1+区损伤后备用视觉区域中的RFs是如何组织的。然而，为了做到这一点，必须改进PRF映射方法，以消除在感知盲点边界附近的PRF估计中出现的偏差(图2)。1、5、6)。我们将研究由于V1+损害和年龄匹配的对照组而导致的慢性偏盲和象限视的患者队列。具体目标#1将开发一种估计PRF地形的直接方法，该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，慢性V1+病变受试者的视野表现和备用视区的PRF特性如何不同。从知觉暗点内的视野位置调整备用视区的能力将识别更适合康复的位置。具体目标#3将检验这一假说，即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度来提高成绩。这种影响在训练前可以视觉上调节hV5/MT+区域的暗点区域尤其强烈(SA#2)。总体而言，我们的方法将描述下游地区如何适应慢性V1+损伤，并将提出新的方法来指导未来的康复训练。

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.