Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia.
J Neural Eng. 2013 Jun;10(3):036013. doi: 10.1088/1741-2560/10/3/036013. Epub 2013 Apr 23.
Visual prostheses currently in development aim to restore some form of vision to patients suffering from diseases such as age-related macular degeneration and retinitis pigmentosa. Most rely on electrically stimulating inner retinal cells via electrodes implanted on or near the retina, resulting in percepts of light termed 'phosphenes'. Activation of spatially distinct populations of cells in the retina is key for pattern vision to be produced. To achieve this, the electrical stimulation must be localized, activating cells only in the direct vicinity of the stimulating electrode(s). With this goal in mind, a hexagonal return (hexapolar) configuration has been proposed as an alternative to the traditional monopolar or bipolar return configurations for electrically stimulating the retina. This study investigated the efficacy of the hexapolar configuration in localizing the activation of retinal ganglion cells (RGCs), compared to a monopolar configuration.
Patch-clamp electrophysiology was used to measure the activation thresholds of RGCs in whole-mount rabbit retina to monopolar and hexapolar electrical stimulation, applied subretinally.
Hexapolar activation thresholds for RGCs located outside the hex guard were found to be significantly (>2 fold) higher than those located inside the area of tissue bounded by the hex guard. The hexapolar configuration localized the activation of RGCs more effectively than its monopolar counterpart. Furthermore, no difference in hexapolar thresholds or localization was observed when using cathodic-first versus anodic-first stimulation.
The hexapolar configuration may provide an improved method for electrically stimulating spatially distinct populations of cells in retinal tissue.
目前正在开发的视觉假体旨在为患有年龄相关性黄斑变性和色素性视网膜炎等疾病的患者恢复某种形式的视力。大多数假体通过植入视网膜上或附近的电极来刺激内视网膜细胞，从而产生称为“光幻视”的光知觉。视网膜中细胞的空间区分群体的激活对于产生模式视觉至关重要。为了实现这一目标，电刺激必须是局部的，仅激活刺激电极（多个）直接附近的细胞。考虑到这一目标，已经提出了六边形返回（六极）配置作为替代传统的单极或双极返回配置来刺激视网膜的方法。本研究调查了六极配置与单极配置相比在定位视网膜神经节细胞（RGC）激活方面的效果。
使用膜片钳电生理学测量兔视网膜全层培养物中单极和六极电刺激下 RGC 的激活阈值，亚视网膜应用。
发现位于六边形保护区外的 RGC 的六极激活阈值明显（>2 倍）高于位于六边形保护区内的组织区域的激活阈值。六极配置比其单极对应物更有效地定位 RGC 的激活。此外，当使用阴极首先与阳极首先刺激时，六极阈值或定位没有差异。
六极配置可能为刺激视网膜组织中空间上不同的细胞群体提供了一种改进的方法。
