The Bionics Institute, East Melbourne, VIC, 3002, Australia.
Department of Surgery (Otolaryngology), University of Melbourne, The Royal Victorian Eye and Ear Hospital, East Melbourne, VIC, 3002, Australia.
J Neural Eng. 2020 Nov 4;17(5):056046. doi: 10.1088/1741-2552/abbff0.
Compared to electrical stimulation, optogenetic stimulation has the potential to improve the spatial precision of neural activation in neuroprostheses, but it requires intense light and has relatively poor temporal kinetics. We tested the effect of hybrid stimulation, which is the combination of subthreshold optical and electrical stimuli, on spectral and temporal fidelity in the cochlea by recording multiunit activity in the inferior colliculus of channelrhodopsin (H134R variant) transgenic mice.
Pulsed light or biphasic electrical pulses were delivered to cochlear spiral ganglion neurons of acutely deafened mice, either as individual stimuli or as hybrid stimuli for which the timing of the electrical pulse had a varied delay relative to the start of the optical pulse. Response thresholds, spread of activation and entrainment data were obtained from multi-unit recordings from the auditory midbrain.
Facilitation occurred when subthreshold electrical stimuli were applied at the end of, or up to 3.75 ms after subthreshold optical pulses. The spread of activation resulting from hybrid stimulation was significantly narrower than electrical-only and optical-only stimulation (p < 0.01), measured at equivalent suprathreshold levels of loudness that are relevant to cochlear implant users. Furthermore, temporal fidelity, measured as maximum following rates to 300 ms pulse trains bursts up to 240 Hz, was 2.4-fold greater than optical-only stimulation (p < 0.05).
By significantly improving spectral resolution of electrical- and optical-only stimulation and the temporal fidelity of optical-only stimulation, hybrid stimulation has the potential to increase the number of perceptually independent stimulating channels in a cochlear implant.
与电刺激相比，光遗传学刺激有可能提高神经假体中神经激活的空间精度，但它需要高强度的光，并且具有相对较差的时间动力学。我们通过记录通道视紫红质（H134R 变体）转基因小鼠下丘脑中的多单位活动，测试了亚阈值光和电刺激相结合的混合刺激对耳蜗中光谱和时间保真度的影响。
在急性耳聋的小鼠耳蜗螺旋神经节神经元中，分别施加脉冲光或双相电脉冲，或者将电脉冲的时间相对于光脉冲的开始有变化的延迟的混合刺激施加到电脉冲中。从中耳的多单位记录中获得响应阈值、激活扩展和激发数据。
当亚阈值电刺激施加在亚阈值光脉冲之后或最多 3.75 毫秒时，会发生易化。与耳蜗植入物使用者相关的等效阈上响度水平下，混合刺激产生的激活扩展明显小于仅电刺激和仅光刺激（p<0.01）。此外，以 300 ms 脉冲串突发高达 240 Hz 的最大跟随率测量的时间保真度比仅光刺激高 2.4 倍（p<0.05）。
通过显著提高电刺激和光刺激的光谱分辨率以及光刺激的时间保真度，混合刺激有可能增加耳蜗植入物中感知独立刺激通道的数量。
