Lightweight and head-mountable scanning nonlinear fiberscope technologies offer an exciting opportunity for enabling mechanistic exploration of ensemble neural activities with subcellular resolution on freely behaving rodents. The tether of the fiberscope, consisting of an optical fiber and scanner drive wires, however, restricts the mouse’s movement and consequently precludes free rotation and limits the freedom of walking. Here we present the first twist-free two-photon fiberscope technology for enabling neuroimaging on freely rotating/walking mice. The technology equips a scanning fiberscope with active rotational tracking and compensation capabilities through an optoelectrical commutator (OEC) to allow the animal to rotate and walk in arbitrary patterns during two-photon fluorescence (TPF) imaging of neural activities. The OEC provides excellent optical coupling stability (${\lt}{{\pm 1}}\%$ fluctuation during rotation) and an extremely high torque sensitivity (${\lt}{{8}}\;{\rm{mN}} \cdot {\rm{m}}$). In addition, the new technology is equipped with a custom grating and prism to effectively manage the temporal properties of the femtosecond excitation pulses through the fiber-optic system, which improved neuroimaging signal by more than ${\rm{2X}}$. This TPF fiberscope imaging platform has been tested for in vivo imaging, and the results demonstrate that it enables reliable recording of calcium dynamics of more than 50 neurons simultaneously in the motor cortices of freely behaving mice in a twist-free fashion. With active tracking function of the OEC enabled, we observed considerable increase in both behavior and neural activities in the motor cortices of the mice during freely behaving neuroimaging experiments.

中文翻译：

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无扭曲超轻双光子纤维镜，可对自由旋转/行走的小鼠进行神经成像

轻量级和头戴式扫描非线性纤维镜技术提供了一个令人兴奋的机会，可以在自由行为的啮齿动物上以亚细胞分辨率对整体神经活动进行机械探索。然而，由光纤和扫描仪驱动线组成的纤维镜的系绳限制了鼠标的移动，因此阻止了自由旋转并限制了行走的自由。在这里，我们展示了第一个无扭曲双光子纤维镜技术，用于在自由旋转/行走的小鼠上实现神经成像。该技术通过光电换向器 (OEC) 为扫描纤维镜配备了主动旋转跟踪和补偿功能，允许动物在神经活动的双光子荧光 (TPF) 成像期间以任意模式旋转和行走。${\lt}{{\pm 1}}\%$旋转期间波动）和极高的扭矩灵敏度（${\lt}{{8}}\;{\rm{mN}} \cdot {\rm {m}}$）。此外，新技术配备了定制光栅和棱镜，可通过光纤系统有效管理飞秒激发脉冲的时间特性，从而将神经影像信号提高了${\rm{2X}}$ 以上。该 TPF 纤维镜成像平台已经过体内测试成像，结果表明它能够以无扭曲的方式同时可靠地记录自由行为小鼠运动皮层中 50 多个神经元的钙动力学。启用 OEC 的主动跟踪功能后，我们观察到在自由行为神经影像学实验中，小鼠运动皮层的行为和神经活动均显着增加。