Departments of Neurosurgery, Ophthalmology, and Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, United States of America.
J Neural Eng. 2019 Apr;16(2):025001. doi: 10.1088/1741-2552/aaeef1. Epub 2018 Nov 7.
Epiretinal prostheses are designed to restore vision in people blinded by photoreceptor degenerative diseases, by directly activating retinal ganglion cells (RGCs) using an electrode array implanted on the retina. In present-day clinical devices, current spread from the stimulating electrode to a distant return electrode often results in the activation of many cells, potentially limiting the quality of artificial vision. In the laboratory, epiretinal activation of RGCs with cellular resolution has been demonstrated with small electrodes, but distant returns may still cause undesirable current spread. Here, the ability of local return stimulation to improve the selective activation of RGCs at cellular resolution was evaluated.
A custom multi-electrode array (512 electrodes, 10 μm diameter, 60 μm pitch) was used to simultaneously stimulate and record from RGCs in isolated primate retina. Stimulation near the RGC soma with a single electrode and a distant return was compared to stimulation in which the return was provided by six neighboring electrodes.
Local return stimulation enhanced the capability to activate cells near the central electrode (<30 μm) while avoiding cells farther away (>30 μm). This resulted in an improved ability to selectively activate ON and OFF cells, including cells encoding immediately adjacent regions in the visual field.
These results suggest that a device that restricts the electric field through local returns could optimize activation of neurons at cellular resolution, improving the quality of artificial vision.
视网膜假体旨在通过在视网膜上植入的电极阵列直接激活视网膜神经节细胞 (RGC)，从而为因光感受器退行性疾病而失明的人恢复视力。在当今的临床设备中，从刺激电极到远侧返回电极的电流扩散通常会导致许多细胞被激活，这可能会限制人工视觉的质量。在实验室中，已经使用小电极证明了具有细胞分辨率的 RGC 的视网膜外激活，但远侧返回仍可能导致不希望的电流扩散。在这里，评估了局部返回刺激改善细胞分辨率下 RGC 选择性激活的能力。
使用定制的多电极阵列（512 个电极，直径 10μm，间距 60μm）同时刺激和记录离体灵长类动物视网膜中的 RGC。比较了在 RGC 胞体附近用单个电极进行刺激和用远侧返回进行刺激，以及用六个相邻电极提供返回的刺激。
局部返回刺激增强了在中央电极附近（<30μm）激活细胞的能力，同时避免了更远的细胞（>30μm）。这导致选择性激活 ON 和 OFF 细胞的能力得到了提高，包括编码视野中相邻区域的细胞。
这些结果表明，一种通过局部返回限制电场的设备可以优化细胞分辨率下神经元的激活，从而提高人工视觉的质量。
