Graduate School of Biomedical Engineering, University of New South Wales, Sydney, NSW 2125, Australia.
J Neurophysiol. 2009 Nov;102(5):2982-93. doi: 10.1152/jn.00545.2009. Epub 2009 Sep 9.
In the last decade several groups have been developing vision prostheses to restore visual perception to the profoundly blind. Despite some promising results from human trials, further understanding of the neural mechanisms involved is crucial for improving the efficacy of these devices. One of the techniques involves placing stimulating electrodes in the subretinal space between the photoreceptor layer and the pigment epithelium to evoke neural responses in the degenerative retina. This study used cell-attached and whole cell current-clamp recordings to investigate the responses of rabbit retinal ganglion cells (RGCs) following subretinal stimulation with 25-mum-diameter electrodes. We found that direct RGC responses with short latency (</=2 ms using 0.1-ms pulses) could be reliably elicited. The thresholds for these responses were reported for on, off, and on-off RGCs over pulse widths 0.1-5.0 ms. During repetitive stimulation these direct activation responses were more readily elicited than responses arising from stimulation of the retinal network. The temporal spiking characteristics of RGCs were characterized as a function of stimulus configurations. We found that the response profiles could be generalized into four classes with distinctive properties. Our results suggest that for subretinal vision prostheses short pulses are preferable for efficacy and safety considerations, and that direct activation of RGCs will be necessary for reliable activation during high-frequency stimulation.
在过去的十年中，许多研究小组一直在开发视觉假体，以恢复深度失明患者的视觉感知。尽管人类试验取得了一些有希望的结果，但进一步了解相关的神经机制对于提高这些设备的效果至关重要。其中一种技术是将刺激电极放置在光感受器层和色素上皮层之间的视网膜下空间，以在变性视网膜中引发神经反应。本研究使用细胞贴附和全细胞电流钳记录来研究使用 25 微米直径的电极进行视网膜下刺激后兔子视网膜神经节细胞 (RGC) 的反应。我们发现，使用 0.1 毫秒的脉冲，可以可靠地引出具有短潜伏期（<=2 毫秒）的直接 RGC 反应。报告了这些反应的阈值，用于在 0.1-5.0 毫秒的脉冲宽度下的 ON、OFF 和 ON-OFF RGC。在重复刺激期间，这些直接激活反应比来自视网膜网络刺激的反应更容易引出。RGC 的时间尖峰特征作为刺激配置的函数进行了表征。我们发现，响应轮廓可以概括为具有独特特性的四个类别。我们的结果表明，对于视网膜下视觉假体，出于功效和安全性考虑，短脉冲是优选的，并且在高频刺激期间，RGC 的直接激活对于可靠激活是必要的。
