Sites of neuronal excitation by epiretinal electrical stimulation
Sites of neuronal excitation by epiretinal electrical stimulation
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DOI：
10.1109/tnsre.2006.870488
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发表时间：
2006-03-01
影响因子：
4.9
通讯作者：
Grill, WM
中科院分区：
文献类型：
--
作者：
Schiefer, MA;Grill, WM
视网膜神经节细胞产生的动作电位最终产生视觉感知。在因色素性视网膜炎和年龄相关性黄斑变性而失明的人中，仍然存在存活的视网膜神经节细胞，并且视网膜可以被电刺激以恢复部分视力。然而，目前还不清楚视网膜中的哪些神经元元素被视网膜外电刺激激活。本研究探讨了细胞的几何形状，电极神经元的距离，刺激持续时间和刺激极性的视网膜神经节细胞与视网膜前电极的兴奋的影响。代表简化的视网膜神经节细胞形态的基于计算机的房室模型提供的证据表明，当电极位于视网膜神经节细胞轴突中的特征性90度弯曲附近时，激发阈值低于当电极位于神经纤维层的经过轴突上方时的激发阈值。这种依赖于电极位置的阈值差异发生在阴极和阳极双相刺激，点源和盘电极，在多个电极到神经元的距离，并在模型的电特性的变化是强大的。这一发现揭示了视网膜神经节细胞的物理几何形状产生强烈依赖于电极位置的刺激阈值。轴突中弯曲附近的低激发阈值将导致电极局部的细胞在比激发经过的轴突所需的电流更低的电流下被激活。这种激活模式提供了一个潜在的解释，如何视网膜前电刺激的结果在生产点，而不是弥漫性或条纹光幻视。
Action potentials arising from retinal ganglion cells ultimately create visual percepts. In persons blind from retinitis pigmentosa and age-related macular degeneration, viable retinal ganglion cells remain, and the retina can be stimulated electrically to restore partial sight. However, it is unclear what neuronal elements in the retina are activated by epiretinal electrical stimulation. This study investigated the effects of cellular geometry, electrode to neuron distance, stimulus duration, and stimulus polarity on excitation of a retinal ganglion cell with an epiretinal electrode. Computer-based compartmental models representing simplified retinal ganglion cell morphology provided evidence that the threshold for excitation was lower when an electrode was located in proximity to the characteristic 90 degrees bend in the axon of the retinal ganglion cell than when it was located over a passing axon of the nerve fiber layer. This electrode-position-dependent difference in threshold occurred with both cathodic and anodic monophasic stimuli, with point source and disk electrodes, at multiple electrode-to-neuron distances, and was robust to changes in the electrical properties of the model. This finding reveals that the physical geometry of the retinal ganglion cells produces stimulation thresholds that depend strongly on electrode position. The low excitation thresholds near the bend in the axon will result in activation of cells local to the electrode at lower currents than required to excite passing axons. This pattern of activation provides a potential explanation of how epiretinal electrical stimulation results in the production of punctuate, rather than diffuse or streaky phosphenes.