Nimmagadda Kiran, Weiland James D
Neuroscience Graduate Program, University of Southern California, Los Angeles, CA, USA.
USC - Caltech MD/PhD Program, Los Angeles, CA, USA.
Transl Vis Sci Technol. 2018 Oct 31;7(5):33. doi: 10.1167/tvst.7.5.33. eCollection 2018 Sep.
Electronic retinal prostheses restore vision in people with outer retinal degeneration by electrically stimulating the inner retina. We characterized visual cortex electrophysiologic response elicited by electrical stimulation of retina in normally sighted and retinal degenerate rats.
Nine normally sighted Long Evans and 11 S334ter line 3 retinal degenerate () rats were used to map cortical responses elicited by epiretinal electrical stimulation in four quadrants of the retina. Six normal and six rats were used to compare the dendritic spine density of neurons in the visual cortex.
The rats required higher stimulus amplitudes to elicit responses in the visual cortex. The cortical electrically evoked responses (EERs) for both healthy and rats show a dose-response characteristic with respect to the stimulus amplitude. The EER maps in healthy rats show retinotopic organization. For rats, cortical retinotopy is not well preserved. The neurons in the visual cortex of rats show a 10% higher dendritic spine density than in the healthy rats.
Cortical activity maps, produced when epiretinal stimulation is applied to quadrants of the retina, exhibit retinotopy in normal but not rats. This is likely due to a combination of degeneration of the retina and increased stimulus thresholds in , which broadens the activated area of the retina.
Loss of retinotopy is evident in rats. If a similar loss of retinotopy is present in humans, retinal prostheses design must include flexibility to account for patient specific variability.
电子视网膜假体通过电刺激视网膜内层来恢复患有外层视网膜变性的人的视力。我们对正常视力和视网膜变性大鼠视网膜电刺激引发的视觉皮层电生理反应进行了特征描述。
使用9只正常视力的长 Evans 大鼠和11只S334ter 3型视网膜变性（）大鼠来绘制视网膜四个象限的视网膜外电刺激引发的皮层反应。使用6只正常大鼠和6只大鼠来比较视觉皮层中神经元的树突棘密度。
大鼠需要更高的刺激幅度才能在视觉皮层中引发反应。健康大鼠和大鼠的皮层电诱发反应（EER）在刺激幅度方面均表现出剂量反应特性。健康大鼠的EER图谱显示出视网膜拓扑组织。对于大鼠，皮层视网膜拓扑结构保存不佳。大鼠视觉皮层中的神经元树突棘密度比健康大鼠高10%。
当视网膜外刺激应用于视网膜象限产生的皮层活动图谱在正常大鼠中显示出视网膜拓扑结构，但在大鼠中则不然。这可能是由于视网膜变性和大鼠刺激阈值增加的综合作用，从而扩大了视网膜的激活区域。
大鼠中视网膜拓扑结构丧失明显。如果人类中存在类似的视网膜拓扑结构丧失，视网膜假体设计必须包括灵活性以考虑患者的个体差异。
