Ryu Sang Baek, Fried Shelley I
Annu Int Conf IEEE Eng Med Biol Soc. 2018 Jul;2018:2458-2461. doi: 10.1109/EMBC.2018.8512795.
Retinal implants offered the promise of restoring functional vision to the blind via the delivery of electrical stimulation to the retina. To enhance the efficacy of these devices, stimulation should elicit neural responses that are similar to the responses that occur naturally in the retina as these have the best chance of carrying a robust signal to visual cortex. A corollary of this is that the responses that arise in visual cortical neurons can be used to compare the effectiveness of different stimulation strategies in the retina. Here, we studied how visual cortical neurons in the mouse respond to monophasic cathodal and anodal electric stimulation delivered via a wire electrode positioned on the outer surface of the eye (extraocular) or within the vitreous cavity of the eye (intraocular). Responses of visual cortical neurons were recorded from primary visual cortex on the side contralateral to the stimulatated eye. For both stimulation modalities, response patterns consisted of a brief burst of spikes followed by a 400-500 ms period of inhibition. Both modalities also elicited stronger responses to cathodal stimuli (vs. anodal). The preferential sensitivity to cathodal stimuli is similar to that of epiretinal stimulation (anodal stimuli are more effective with sub-retinal stimulation) suggest the extraocular approach mirrors epiretinal stimulation. Extraocular stimulation also showed some response characteristics that were different from those observed in the retina, e.g., at very strong amplitudes, cathodal and anodal stimulation produced similar responses.
视网膜植入物有望通过向视网膜传递电刺激，为盲人恢复功能性视力。为提高这些设备的功效，刺激应引发与视网膜中自然发生的反应相似的神经反应，因为这些反应最有可能将强大的信号传递到视觉皮层。由此得出的一个推论是，视觉皮层神经元产生的反应可用于比较视网膜中不同刺激策略的有效性。在此，我们研究了小鼠视觉皮层神经元如何对通过置于眼外表面（眼外）或眼玻璃体内（眼内）的线电极施加的单相阴极和阳极电刺激作出反应。在受刺激眼对侧的初级视觉皮层记录视觉皮层神经元的反应。对于这两种刺激方式，反应模式均包括短暂的尖峰爆发，随后是400 - 500毫秒的抑制期。两种方式对阴极刺激（相对于阳极刺激）也引发更强的反应。对阴极刺激的优先敏感性与视网膜外刺激相似（阳极刺激在视网膜下刺激时更有效），这表明眼外方法反映了视网膜外刺激。眼外刺激还表现出一些与在视网膜中观察到的不同的反应特征，例如，在非常强的振幅下，阴极和阳极刺激产生相似的反应。
