Neuroscience Graduate Program, University of Southern California, Los Angeles, California 90033, USA.
Invest Ophthalmol Vis Sci. 2011 Feb 1;52(1):549-57. doi: 10.1167/iovs.10-5282. Print 2011 Jan.
Since 2002, six blind patients have undergone implantation of an epiretinal 4 × 4 electrode array designed to directly stimulate the remaining cells of the retina after severe photoreceptor degeneration due to retinitis pigmentosa. This study was conducted to investigate how the brightness of percepts is affected by pulse timing across electrodes in two of these patients.
Subjects compared the perceived brightness of a standard stimulus (synchronous pulse trains presented across pairs of electrodes) to the perceived brightness of a test stimulus (pulse trains across the electrode pair phase shifted by 0.075, 0.375, 1.8, or 9 ms). The current amplitude necessary for each phase-shifted test stimulus to match the brightness of the standard was determined.
Depending on the electrode pair, interactions between electrodes were either facilitatory (the perceived brightness produced by stimulating the pair of electrodes was greater than that produced by stimulating either electrode alone) or suppressive (the perceived brightness produced by stimulating the pair of electrodes was less than that produced by stimulating either electrode alone). The amount of interaction between electrodes decreased as a function of increased separation both in time (the phase-shift between pulse trains) and space (center-to-center distance between the electrode pair).
For visual prostheses to represent visual scenes that are changing in both space and time requires the development of spatiotemporal models describing the effects of stimulation across multiple electrodes. During multielectrode stimulation, interactions between electrodes have a significant influence on subjective brightness that includes both facilitatory and suppressive effects, and these interactions can be described with a simple computational model. (ClinicalTrials.gov number, NCT00279500.).
自 2002 年以来，六名因色素性视网膜炎导致严重光感受器变性而失明的患者接受了一种 4×4 电极的视网膜内植入物的植入，该植入物旨在直接刺激视网膜剩余细胞。本研究旨在调查在这两名患者中的两名患者中，电极之间的脉冲定时如何影响感知的亮度。
受试者将标准刺激（跨对电极呈现的同步脉冲串）与测试刺激（跨电极对相移 0.075、0.375、1.8 或 9 ms 的脉冲串）的感知亮度进行比较。确定每个相移测试刺激所需的电流幅度，以使亮度与标准刺激匹配。
根据电极对的不同，电极之间的相互作用要么是促进性的（刺激电极对产生的感知亮度大于单独刺激任一电极产生的感知亮度），要么是抑制性的（刺激电极对产生的感知亮度小于单独刺激任一电极产生的感知亮度）。电极之间的相互作用量随着时间（脉冲串之间的相位差）和空间（电极对中心到中心的距离）的增加而减少。
为了使视觉假体代表在空间和时间上都在变化的视觉场景，需要开发描述多个电极刺激效果的时空模型。在多电极刺激期间，电极之间的相互作用对主观亮度有显著影响，包括促进和抑制作用，并且可以使用简单的计算模型来描述这些相互作用。（临床试验.gov 编号，NCT00279500）。
