Neurophysics, NMI Natural and Medical Sciences Institute at the University Tübingen, Reutlingen, Germany.
Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany.
J Neural Eng. 2021 Jun 17;18(4). doi: 10.1088/1741-2552/ac0679.
. Most neuroprosthetic implants employ pulsatile square-wave electrical stimuli, which are significantly different from physiological inter-neuronal communication. In case of retinal neuroprosthetics, which use a certain type of pulsatile stimuli, reliable object and contrast discrimination by implanted blind patients remained challenging. Here we investigated to what extent simple objects can be discriminated from the output of retinal ganglion cells (RGCs) upon sinusoidal stimulation.. Spatially confined objects were formed by different combinations of 1024 stimulating microelectrodes. The RGC activity in theretina of photoreceptor-degenerated mouse, of healthy mouse or of primate was recorded simultaneously using an interleaved recording microelectrode array implemented in a CMOS-based chip.. We report that application of sinusoidal electrical stimuli (40 Hz) in epiretinal configuration instantaneously and reliably modulates the RGC activity in spatially confined areas at low stimulation threshold charge densities (40 nC mm). Classification of overlapping but spatially displaced objects (1° separation) was achieved by distinct spiking activity of selected RGCs. A classifier (regularized logistic regression) discriminated spatially displaced objects (size: 5.5° or 3.5°) with high accuracy (90% or 62%). Stimulation with low artificial contrast (10%) encoded by different stimulus amplitudes generated RGC activity, which was classified with an accuracy of 80% for large objects (5.5°).. We conclude that time-continuous smooth-wave stimulation provides robust, localized neuronal activation in photoreceptor-degenerated retina, which may enable future artificial vision at high temporal, spatial and contrast resolution.
. 大多数神经假体植入物采用脉冲方波电刺激，这与生理神经元间的通讯有很大的不同。在视网膜神经假体中，使用某种类型的脉冲刺激时，植入的盲人可靠地区分目标和对比度仍然具有挑战性。在这里，我们研究了在正弦波刺激下，通过视网膜神经节细胞（RGC）的输出，简单物体可以在多大程度上被区分开来。. 通过不同的组合形成了空间受限的物体，使用了 1024 个刺激微电极。使用在基于 CMOS 的芯片中实现的交错记录微电极阵列，同时记录了光感受器退化的小鼠、健康小鼠或灵长类动物视网膜中的 RGC 活动。. 我们报告说，在视网膜上应用正弦电刺激（40 Hz）可以在低刺激阈值电荷密度（40 nC mm）下，瞬间可靠地调制空间受限区域中的 RGC 活动。通过选择的 RGC 的独特放电活动，可以对重叠但空间移位的物体（1°分离）进行分类。分类器（正则化逻辑回归）以高准确性（90%或 62%）区分空间移位的物体（大小：5.5°或 3.5°）。用不同的刺激幅度产生的低人工对比度（10%）刺激，以 80%的准确率对大物体（5.5°）进行分类。. 我们得出的结论是，连续的平滑波刺激为光感受器退化的视网膜提供了稳健、局部的神经元激活，这可能使未来的人工视觉具有更高的时间、空间和对比度分辨率。
