Feasibility of a visual prosthesis for the blind based on intracortical microstimulation of the visual cortex
Feasibility of a visual prosthesis for the blind based on intracortical microstimulation of the visual cortex
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DOI：
10.1093/brain/119.2.507
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发表时间：
1996-04-01
期刊：
影响因子：
14.5
通讯作者：
Vallabhanath, P
中科院分区：
文献类型：
--
作者：
Schmidt, EM;Bak, MJ;Vallabhanath, P
本文研究了一名因青光眼而完全失明22年的42岁女性，利用视觉皮质内微刺激（ICMS）为盲人制作视觉假体的可行性。38个微电极植入右侧视觉皮层，靠近枕极，为期4个月。38个植入的微电极中有34个产生了被称为光幻视的小光点。双相脉冲序列产生磷光的阈值电流低至1.9 μ A，大多数微电极的阈值低于25 μ A，磷光亮度可随刺激幅度、频率和脉冲持续时间的变化而改变。在几分钟的时间内反复刺激会使光幻视亮度逐渐下降。光幻灯不闪烁。光幻视的大小从“针尖”到“镍币”（直径20毫米的硬币）不等。磷光烯的大小通常随刺激电流的增加而减小，但随训练长度的增加而略有增加。在接近阈值的刺激水平下，光幻视经常被报道有颜色。随着刺激水平的增加，光幻视普遍呈白色、灰色或黄色。个体光幻视出现在与受试者的不同距离。当两个光烯同时产生时，单个光烯的视距离有时会发生变化，使它们看起来大约在相同的距离上。当三个或更多的光幻视同时产生时，它们是共面的。除了狂欢场合，光幻视在刺激训练结束时迅速消失。当刺激TLs增加到1 s以上时，光幻视通常在训练结束前消失。通过中断长时间的刺激训练并在刺激中短暂停顿，可以增加光幻视感知的持续时间。间隔500 μ m的皮质内微电极产生单独的磷幻视，但间隔250 μ m的微电极通常不会产生单独的磷幻视。与地面压裂相比，这种两点的分辨率提高了约五倍。在一些单独的微电极上，有时通过增加刺激电流产生第二个紧密间隔的光幻灯，光幻灯随着眼球运动而移动。当多达六个光幻视同时被激发时，它们在眼球运动时都以相同的相对方向运动。所有的光幻视都位于左半场，大部分位于水平子午线以上，大部分光幻视聚集在一个相对较小的视觉空间区域内。与表面刺激相比，ICMS潜在的更大的微电极密度和更低的功率要求对于视觉假体来说是令人鼓舞的。然而，在建立基于ICMS的视觉假体的可行性之前，还需要对盲人受试者进行进一步的研究，优化刺激参数，测试复杂的图像识别。
The feasibility of producing a visual prosthesis for the blind using intracortical microstimulation (ICMS) of the visual cortex was studied in a 42-year-old woman who had been totally blind for 22 years secondary to glaucoma. Thirty-eight microelectrodes were implanted in the right visual cortex, near the occipital pole, for a period of 4 months. Percepts reported as small spots of light, called phosphenes, were produced with 34 of the 38 implanted microelectrodes. Threshold currents for phosphene generation with trains of biphasic pulses were as low as 1.9 mu A, and most of the microelectrodes had thresholds below 25 mu A. Phosphene brightness could be modified with stimulus amplitude, frequency and pulse duration. Repeated stimulation over a period of minutes produced a gradual decrease in phosphene brightness. Phosphenes did not flicker. The apparent size of phosphenes ranged from a 'pin-point' to a 'nickel' (20 mm diameter coin) held at arm's length. Phosphene size usually decreased as stimulation current was increased but increased slightly as the train length (TL) was increased. At levels of stimulation near threshold, the phosphenes were often reported to have colours. As the stimulation level was increased, the phosphenes generally became white, greyish or yellowish. Individual phosphenes appeared at different distances from the subject. When two phosphenes were simultaneously generated, the apparent distances of the individual phosphenes sometimes changed to make them appear to be at about the same distance. When three or more phosphenes were simultaneously generated, they became coplanar Except for rave occasions, phosphenes extinguished rapidly at the termination of the stimulation train. When stimulation TLs were increased beyond 1 s, phosphenes usually disappeared before the end of the train. The duration of phosphene perception could be increased by interrupting a long stimulation train with brief pauses in stimulation. Intracortical microelectrodes spaced 500 mu m apart generated separate phosphenes, but microelectrodes spaced 250 mu m typically did not. This two-point resolution was about Jive times closer than has typically been achieved with surface stimulation. With some individual microelectrodes, a second closely spaced phosphene was sometimes produced by increasing the stimulation current Phosphenes moved with eye movements. When up to six phosphenes were simultaneously elicited, they all moved with the same relative orientation during eye movements. All phosphenes were located in the left hemi-field with the majority above the horizontal meridian There was a clustering of most of the phosphenes within a relatively small area of visual space. The potentially greater microelectrode density and lower power requirements of ICMS compared with surface stimulation appears encouraging for a visual prosthesis. However, further studies with blind subjects are required to optimize stimulation parameters and test complex image recognition before the feasibility of a visual prosthesis based on ICMS can be established.