Plank Tina, Frolo Jozef, Brandl-Rühle Sabine, Renner Agnes B, Jägle Herbert, Greenlee Mark W
*PhD †MSc ‡MD Institute of Psychology, University of Regensburg, Regensburg, Germany (TP, JF, MWG); and Department of Ophthalmology, University Medical Center Regensburg, Regensburg, Germany (SB-R, ABR, HJ).
Optom Vis Sci. 2017 Mar;94(3):297-310. doi: 10.1097/OPX.0000000000001047.
In patients with central visual field scotomata, a large part of visual cortex is not adequately stimulated. Patients often use a new eccentric fixation area on intact peripheral retina ("preferred retinal locus"-PRL) that functions as a pseudo-fovea. We used functional magnetic resonance imaging (fMRI) to examine whether stimulating this pseudo-fovea leads to increased activation or altered activation patterns in visual cortex in comparison to stimulating a comparable peripheral area in the opposite hemifield (OppPRL).
Nineteen patients with binocular central scotomata caused by hereditary retinal dystrophies and an age-matched control group were tested. The center of the visual field, PRL, and OppPRL were stimulated with flickering checkerboard stimuli and object pictures during fMRI measurement.
Results show that stimulation with pictures of everyday objects led to overall larger BOLD (blood oxygen level dependent) responses in visual cortex compared to that evoked by stimulation with flickering checkerboards. Patients showed this enhancement as early as in V1. When the PRL was directly stimulated with object pictures, the central representation area in early visual cortex was coactivated in the patients but not in the controls. In higher visual areas beyond retinotopic cortex, BOLD responses to stimulation of the PRL with object pictures were significantly enhanced in comparison to stimulation of the OppPRL area. Highly stable eccentric fixation with the PRL was associated with a higher BOLD signal in visual cortex in patients, and this effect was most pronounced in the conditions with object picture stimulation.
The observed results suggest that naturalistic images are more likely to trigger top-down processes that regulate activation in early visual cortex in patients with central vision loss.
在患有中心视野暗点的患者中，大部分视觉皮层未得到充分刺激。患者常使用完整周边视网膜上的一个新的偏心注视区域（“首选视网膜位点”-PRL），其起到假中央凹的作用。我们使用功能磁共振成像（fMRI）来检查与刺激对侧半视野中的可比周边区域（对侧PRL，OppPRL）相比，刺激这个假中央凹是否会导致视觉皮层激活增加或激活模式改变。
对19名由遗传性视网膜营养不良导致双眼中心暗点的患者和一个年龄匹配的对照组进行测试。在fMRI测量期间，用闪烁棋盘格刺激和物体图片刺激视野中心、PRL和OppPRL。
结果表明，与闪烁棋盘格刺激所诱发的反应相比，日常物体图片刺激在视觉皮层中导致总体上更大的血氧水平依赖（BOLD）反应。患者早在V1区就出现了这种增强。当用物体图片直接刺激PRL时，早期视觉皮层中的中央表征区域在患者中被共同激活，而在对照组中未被激活。在视网膜拓扑皮层以外的更高视觉区域，与刺激OppPRL区域相比，用物体图片刺激PRL时的BOLD反应显著增强。患者高度稳定地使用PRL进行偏心注视与视觉皮层中更高的BOLD信号相关，并且这种效应在物体图片刺激的条件下最为明显。
观察结果表明，自然主义图像更有可能触发自上而下的过程，从而调节中心视力丧失患者早期视觉皮层的激活。
