Neurocomputing and Neurorobotics Research Group, Complutense University of Madrid Madrid, Spain.
Front Neurosci. 2011 Jul 5;5:84. doi: 10.3389/fnins.2011.00084. eCollection 2011.
Most work on visual prostheses has centered on developing retinal or cortical devices. However, when retinal implants are not feasible, neuroprostheses could be implanted in the lateral geniculate nucleus (LGN) of the thalamus, the intermediate relay station of visual information from the retina to the visual cortex (V1). The objective of the present study was to determine the types of artificial stimuli that when delivered to the visual thalamus can generate reliable responses of the cortical neurons similar to those obtained when the eye perceives a visual image. Visual stimuli {S(i)} were presented to one eye of an experimental animal and both, the thalamic {RTh(i)} and cortical responses {RV1(i)} to such stimuli were recorded. Electrical patterns {RTh(i)} resembling {RTh(i)} were then injected into the visual thalamus to obtain cortical responses {RV1(i)} similar to {RV1(i)}. Visually- and electrically generated V1 responses were compared.
During the course of this work we: (i) characterized the response of V1 neurons to visual stimuli according to response magnitude, duration, spiking rate, and the distribution of interspike intervals; (ii) experimentally tested the dependence of V1 responses on stimulation parameters such as intensity, frequency, duration, etc., and determined the ranges of these parameters generating the desired cortical activity; (iii) identified similarities between responses of V1 useful to compare the naturally and artificially generated neuronal activity of V1; and (iv) by modifying the stimulation parameters, we generated artificial V1 responses similar to those elicited by visual stimuli. Generation of predictable and consistent phosphenes by means of artificial stimulation of the LGN is important for the feasibility of visual prostheses. Here we proved that electrical stimuli to the LGN can generate V1 neural responses that resemble those elicited by natural visual stimuli.
大多数视觉假体的研究都集中在开发视网膜或皮质设备上。然而，当视网膜植入物不可行时，神经假体可以植入丘脑的外侧膝状体核（LGN），这是视网膜到视觉皮层（V1）的视觉信息的中间中继站。本研究的目的是确定当施加于视觉丘脑时可以产生类似于眼睛感知视觉图像时获得的皮质神经元的可靠反应的人工刺激的类型。向实验动物的一只眼睛呈现视觉刺激{S(i)}，并记录对这种刺激的丘脑{RTh(i)}和皮质反应{RV1(i)}。然后将类似于{RTh(i)}的电模式{RTh(i)}注入视觉丘脑以获得类似于{RV1(i)}的皮质反应{RV1(i)}。比较了视觉和电产生的 V1 反应。
在这项工作的过程中，我们：（i）根据反应幅度、持续时间、尖峰率和尖峰间隔分布来描述 V1 神经元对视觉刺激的反应；（ii）根据强度、频率、持续时间等刺激参数实验测试了 V1 反应的依赖性，并确定了产生所需皮质活动的这些参数的范围；（iii）确定了 V1 反应之间的相似性，这些相似性有助于比较 V1 的自然和人工产生的神经元活动；（iv）通过修改刺激参数，我们生成了类似于视觉刺激引起的人工 V1 反应。通过人工刺激 LGN 产生可预测和一致的光幻视对于视觉假体的可行性很重要。在这里，我们证明了 LGN 的电刺激可以产生类似于自然视觉刺激引起的 V1 神经反应。
