Boinagrov David, Pangratz-Fuehrer Susanne, Goetz Georges, Palanker Daniel
Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305, USA. Department of Physics, Stanford University, Stanford, CA 94305, USA.
J Neural Eng. 2014 Apr;11(2):026008. doi: 10.1088/1741-2560/11/2/026008. Epub 2014 Mar 10.
Intra-retinal placement of stimulating electrodes can provide close and stable proximity to target neurons. We assessed improvement in stimulation thresholds and selectivity of the direct and network-mediated retinal stimulation with intraretinal electrodes, compared to epiretinal and subretinal placements.
Stimulation thresholds of the retinal ganglion cells (RGCs) in wild-type rat retina were measured using the patch-clamp technique. Direct and network-mediated responses were discriminated using various synaptic blockers.
Three types of RGC responses were identified: short latency (SL, τ < 5 ms) originating in RGCs, medium latency (ML, 3 < τ < 70 ms) originating in the inner nuclear layer and long latency (LL, τ > 40 ms) originating in photoreceptors. Cathodic epiretinal stimulation exhibited the lowest threshold for direct RGC response and the highest direct selectivity (network/direct thresholds ratio), exceeding a factor of 3 with pulse durations below 0.5 ms. For network-mediated stimulation, the lowest threshold was obtained with anodic pulses in OPL position, and its network selectivity (direct/network thresholds ratio) increased with pulse duration, exceeding a factor of 4 at 10 ms. Latency of all three types of responses decreased with increasing strength of the stimulus.
These results define the optimal range of pulse durations, pulse polarities and electrode placement for the retinal prostheses aiming at direct or network-mediated stimulation of RGCs.
将刺激电极置于视网膜内可使其与靶神经元紧密且稳定地靠近。我们评估了与视网膜上和视网膜下放置电极相比，视网膜内电极在直接和网络介导的视网膜刺激方面刺激阈值和选择性的改善情况。
使用膜片钳技术测量野生型大鼠视网膜中视网膜神经节细胞（RGCs）的刺激阈值。使用各种突触阻滞剂区分直接和网络介导的反应。
确定了三种类型的RGC反应：起源于RGCs的短潜伏期（SL，τ<5毫秒）、起源于内核层的中潜伏期（ML，3<τ<70毫秒）和起源于光感受器的长潜伏期（LL，τ>40毫秒）。阴极视网膜上刺激对直接RGC反应表现出最低阈值和最高直接选择性（网络/直接阈值比），在脉冲持续时间低于0.5毫秒时超过3倍。对于网络介导的刺激，在OPL位置使用阳极脉冲获得最低阈值，其网络选择性（直接/网络阈值比）随脉冲持续时间增加，在10毫秒时超过4倍。所有三种反应类型的潜伏期随刺激强度增加而缩短。
这些结果确定了旨在直接或网络介导刺激RGCs的视网膜假体的最佳脉冲持续时间、脉冲极性和电极放置范围。
