Bionics Institute, East Melbourne, Victoria, Australia.
Invest Ophthalmol Vis Sci. 2012 Sep 19;53(10):6291-300. doi: 10.1167/iovs.12-9434.
The aim of this study was to compare simultaneous stimulation of multiple electrodes to single-electrode stimulation in a retinal prosthesis.
A platinum electrode array was implanted into the suprachoroidal space in six normally sighted anesthetized cats. Multiunit activity from the primary visual cortex in response to retinal stimulation was recorded. Cortical thresholds, yield of responses, dynamic ranges, and the spread of retinal activation were measured for three modes of stimulation: single electrode, half-row (six-electrode horizontal line), and column (seven-electrode vertical line).
Stimulation of the best half-rows and columns was found to elicit activity with higher yield and lower charge thresholds per electrode compared to the best single electrodes. Dynamic ranges between the three modes were similar. As expected, peak voltages measured for columns and half-rows were lower than those measured for single electrodes. Spread of retinal activation, determined by the increase in threshold with distance in the retina from the best site, was found to be similar between single- and multiple-electrode stimulation but dependent on orientation.
The lower thresholds, higher yield, equivalent dynamic ranges, and equivalent spread of retinal activation observed from simultaneous stimulation of multiple electrodes may be due to current and/or neural summation within the retina. Such stimulation techniques could be useful for the presentation of lines and edges of objects using a suprachoroidal retinal stimulator with low voltage compliance. Furthermore, the results suggest that more complex visual processing strategies in addition to sequential stimulation of individual electrodes should be considered for retinal prostheses.
本研究旨在比较视网膜假体中单电极刺激与多电极刺激的效果。
将铂电极阵列植入六只正常视力麻醉猫的脉络膜上腔。记录初级视皮层对视网膜刺激的多单位活动。测量三种刺激模式（单电极、半排（六电极水平线）和列（七电极垂直线）的皮质阈值、响应率、动态范围和视网膜激活的扩展。
与最佳单电极相比，最佳半排和列的刺激被发现能以更高的响应率和更低的每个电极的电荷量阈值来引发活动。三种模式之间的动态范围相似。如预期的那样，列和半排的峰值电压低于单电极的峰值电压。通过测量视网膜从最佳部位的距离增加引起的阈值来确定视网膜激活的扩展，发现单电极和多电极刺激之间的扩展相似，但取决于方向。
多电极同时刺激引起的较低阈值、较高响应率、等效动态范围和等效视网膜激活扩展可能是由于视网膜内的电流和/或神经总和。这种刺激技术可用于使用具有低电压顺应性的脉络膜上视网膜刺激器呈现物体的线条和边缘。此外，结果表明，除了单个电极的顺序刺激之外，还应该考虑视网膜假体中的更复杂的视觉处理策略。
