Non-Scanning Fiber-Optic Near-Infrared Beam Led to Two-Photon Optogenetic Stimulation In-Vivo

Stimulation of specific neurons expressing opsins in a targeted region to manipulate brain function has proved to be a powerful tool in neuroscience. However, the use of visible light for optogenetic stimulation is invasive due to low penetration depth and tissue damage owing to larger absorption and scattering. Here, we report, for the first time, in-depth non-scanning fiber-optic two-photon optogenetic stimulation (FO-TPOS) of neurons in-vivo in transgenic mouse models. In order to optimize the deep-brain stimulation strategy, we characterized two-photon activation efficacy at different near-infrared laser parameters. The significantly-enhanced in-depth stimulation efficiency of FO-TPOS as compared to conventional single-photon beam was demonstrated both by experiments and Monte Carlo simulation. The non-scanning FO-TPOS technology will lead to better understanding of the in-vivo neural circuitry because this technology permits more precise and less invasive anatomical delivery of stimulation.

在靶向脑区中刺激表达视蛋白（opsins）的特定神经元以调控脑功能，已被证实是神经科学领域极具应用价值的研究工具。然而，可见光用于光遗传刺激（optogenetic stimulation）时，因穿透深度有限，且受较强的吸收与散射作用会引发组织损伤，因此具有侵入性。本研究首次报道了在转基因小鼠模型体内，对神经元开展无扫描光纤双光子光遗传刺激（fiber-optic two-photon optogenetic stimulation, FO-TPOS）的深层刺激技术。为优化深层脑刺激策略，我们对不同近红外激光参数下的双光子激活效能进行了系统表征。相较于传统单光子光束，FO-TPOS的深层刺激效率得到显著提升，这一结论已通过实验与蒙特卡洛模拟（Monte Carlo simulation）得到验证。该无扫描FO-TPOS技术可实现更为精准且侵入性更低的解剖靶向刺激递送，从而助力研究者更深入地解析体内神经环路。