Frequency and Amplitude Modulation Have Different Effects on the Percepts Elicited by Retinal Stimulation
Frequency and Amplitude Modulation Have Different Effects on the Percepts Elicited by Retinal Stimulation
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DOI：
10.1167/iovs.11-8401
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发表时间：
2012-01-01
影响因子：
4.4
通讯作者：
Weiland, James D.
中科院分区：
文献类型：
--
作者：
Nanduri, Devyani;Fine, Ione;Weiland, James D.
目的。为了恢复功能性形式的视力，通过直接刺激剩余视网膜回路的视网膜前假体被植入到患有晚期视网膜色素变性的受试者身上。在这项研究中，操纵脉冲串的频率和幅度对荧光灯出现的大小和亮度有不同的影响。方法：在9个单独的电极上进行了实验，被试患有严重的RP(2004年植入16通道视网膜前假体)。采用心理物理技术，通过调制电流幅度(恒定频率)或刺激频率(恒定电流幅度)改变双相脉冲串，测量磷烯的亮度和大小。结果：增加刺激频率总是增加亮度，而对激发的膦的大小影响较小。相反，增加刺激幅度通常会增加膦的大小和亮度。这些实验发现可以用一个简单的计算模型来解释，该模型基于先前的心理物理工作和预期的盘状电极电流的空间传播。结论：鉴于幅度和频率对感知大小有可分离的影响，这些发现表明，频率调制在不损失空间分辨率的情况下改善了对大范围亮度级别的编码。未来的视网膜假体设计可能受益于拥有独立操纵脉冲串幅度和频率的灵活性(临床试验.gov编号，NCT00279500)。(投资眼科VS科学。2012年；53：205214)doi：10.1167/iovs.11-8401
PURPOSE. In an effort to restore functional form vision, epiretinal prostheses that elicit percepts by directly stimulating remaining retinal circuitry were implanted in human subjects with advanced retinitis pigmentosa RP). In this study, manipulating pulse train frequency and amplitude had different effects on the size and brightness of phosphene appearance.METHODS. Experiments were performed on a single subject with severe RP (implanted with a 16-channel epiretinal prosthesis in 2004) on nine individual electrodes. Psychophysical techniques were used to measure both the brightness and size of phosphenes when the biphasic pulse train was varied by either modulating the current amplitude (with constant frequency) or the stimulating frequency (with constant current amplitude).RESULTS. Increasing stimulation frequency always increased brightness, while having a smaller effect on the size of elicited phosphenes. In contrast, increasing stimulation amplitude generally increased both the size and brightness of phosphenes. These experimental findings can be explained by using a simple computational model based on previous psychophysical work and the expected spatial spread of current from a disc electrode.CONCLUSIONS. Given that amplitude and frequency have separable effects on percept size, these findings suggest that frequency modulation improves the encoding of a wide range of brightness levels without a loss of spatial resolution. Future retinal prosthesis designs could benefit from having the flexibility to manipulate pulse train amplitude and frequency independently (clinicaltrials.gov number, NCT00279500). (Invest Ophthalmol Vis Sci. 2012;53:205-214) DOI:10.1167/iovs.11-8401