Haak Koen V, Morland Antony B, Rubin Gary S, Cornelissen Frans W
Donders Institute for Brain, Cognition and Behaviour, Centre for Cognitive Neuroimaging, Radboud University, Nijmegen, The Netherlands.
York Neuroimaging Centre, Department of Psychology, University of York, York, UK.
Ophthalmic Physiol Opt. 2016 May;36(3):335-43. doi: 10.1111/opo.12279. Epub 2016 Feb 29.
The eye disease macular degeneration (MD) is a leading cause of blindness worldwide. There is no cure for MD, but several promising treatments aimed at restoring vision at the level of the retina are currently under investigation. These treatments assume that the patient's brain can still process appropriately the retinal input once it is restored, but whether this assumption is correct has yet to be determined.
We used functional magnetic resonance imaging (fMRI) and connective field modelling to determine whether the functional connectivity between the input-deprived portions of primary visual cortex (V1) and early extrastriate areas (V2/3) is still retinotopically organised. Specifically, in both patients with juvenile macular degeneration and age-matched controls with simulated retinal lesions, we assessed the extent to which the V1-referred connective fields of extrastriate voxels, as estimated on the basis of spontaneous fMRI signal fluctuations, adhered to retinotopic organisation.
We found that functional connectivity between the input-deprived portions of visual areas V1 and extrastriate cortex is still largely retinotopically organised in MD, although on average less so than in controls. Patients with stable fixation exhibited normal retinotopic connectivity, however, suggesting that for the patients with unstable fixation, eye-movements resulted in spurious, homogeneous signal modulations across the entire input-deprived cortex, which would have hampered our ability to assess their spatial structure of connectivity.
Despite the prolonged loss of visual input due to MD, the cortico-cortical connections of input-deprived visual cortex remain largely intact. This suggests that the restoration of sight in macular degeneration can rely on a largely unchanged retinotopic representation in early visual cortex following loss of central retinal function.
眼部疾病黄斑变性（MD）是全球失明的主要原因。目前尚无治愈MD的方法，但目前有几种旨在恢复视网膜水平视力的有前景的治疗方法正在研究中。这些治疗方法假定一旦视网膜输入恢复，患者的大脑仍能适当地处理它，但这一假设是否正确尚待确定。
我们使用功能磁共振成像（fMRI）和连接场建模来确定初级视觉皮层（V1）输入缺失部分与早期纹外区域（V2/3）之间的功能连接是否仍保持视网膜拓扑组织。具体而言，在青少年黄斑变性患者和模拟视网膜病变的年龄匹配对照中，我们评估了基于自发fMRI信号波动估计的纹外体素的V1相关连接场在多大程度上遵循视网膜拓扑组织。
我们发现，在MD患者中，视觉区域V1的输入缺失部分与纹外皮层之间的功能连接在很大程度上仍保持视网膜拓扑组织，尽管平均而言不如对照组明显。然而，固定稳定的患者表现出正常的视网膜拓扑连接，这表明对于固定不稳定的患者，眼球运动导致在整个输入缺失皮层出现虚假的、均匀的信号调制，这会妨碍我们评估其连接的空间结构的能力。
尽管由于MD导致视觉输入长期丧失，但输入缺失的视觉皮层的皮质-皮质连接在很大程度上仍保持完整。这表明黄斑变性患者视力的恢复可以依赖于中央视网膜功能丧失后早期视觉皮层中基本不变的视网膜拓扑表征。
