Lorach Henri, Lei Xin, Galambos Ludwig, Kamins Theodore, Mathieson Keith, Dalal Roopa, Huie Philip, Harris James, Palanker Daniel
Hansen Experimental Physics Laboratory, Stanford University, Stanford, California, United States 2Department of Ophthalmology, Stanford University, Stanford, California, United States.
Department of Electrical Engineering, Stanford University, Stanford, California, United States.
Invest Ophthalmol Vis Sci. 2015 Nov;56(12):7444-50. doi: 10.1167/iovs.15-17521.
Prosthetic restoration of partial sensory loss leads to interactions between artificial and natural inputs. Ideally, the rehabilitation should allow perceptual fusion of the two modalities. Here we studied the interactions between normal and prosthetic vision in a rodent model of local retinal degeneration.
Implantation of a photovoltaic array in the subretinal space of normally sighted rats induced local degeneration of the photoreceptors above the chip, and the inner retinal neurons in this area were electrically stimulated by the photovoltaic implant powered by near-infrared (NIR) light. We studied prosthetic and natural visually evoked potentials (VEP) in response to simultaneous stimulation by NIR and visible light patterns.
We demonstrate that electrical and natural VEPs summed linearly in the visual cortex, and both responses decreased under brighter ambient light. Responses to visible light flashes increased over 3 orders of magnitude of contrast (flash/background), while for electrical stimulation the contrast range was limited to 1 order of magnitude. The maximum amplitude of the prosthetic VEP was three times lower than the maximum response to a visible flash over the same area on the retina.
Ambient light affects prosthetic responses, albeit much less than responses to visible stimuli. Prosthetic representation of contrast in the visual scene can be encoded, to a limited extent, by the appropriately calibrated stimulus intensity, which also depends on the ambient light conditions. Such calibration will be important for patients combining central prosthetic vision with natural peripheral sight, such as in age-related macular degeneration.
部分感觉丧失的假体修复会导致人工输入与自然输入之间的相互作用。理想情况下，康复应能实现两种模式的感知融合。在此，我们在局部视网膜变性的啮齿动物模型中研究了正常视觉与假体视觉之间的相互作用。
将光伏阵列植入正常视力大鼠的视网膜下空间，导致芯片上方的光感受器局部变性，该区域的视网膜内层神经元由近红外（NIR）光供电的光伏植入物进行电刺激。我们研究了对NIR和可见光模式同时刺激的假体视觉诱发电位（VEP）和自然视觉诱发电位。
我们证明，电VEP和自然VEP在视觉皮层中线性叠加，并且在较亮的环境光下两种反应均降低。对可见光闪烁的反应在3个数量级的对比度（闪光/背景）范围内增加，而对于电刺激，对比度范围仅限于1个数量级。假体VEP的最大幅度比视网膜上同一区域对可见闪光的最大反应低三倍。
环境光会影响假体反应，尽管其影响远小于对可见刺激的反应。视觉场景中对比度的假体表征可以在一定程度上通过适当校准的刺激强度进行编码，这也取决于环境光条件。这种校准对于将中央假体视觉与自然周边视力相结合的患者（如年龄相关性黄斑变性患者）非常重要。
