An Image-Free Opto-Mechanical System for Creating Virtual Environments and Imaging Neuronal Activity in Freely Moving Caenorhabditis elegans

Non-invasive recording in untethered animals is arguably the ultimate step in the analysis of neuronal function, but such recordings remain elusive. To address this problem, we devised a system that tracks neuron-sized fluorescent targets in real time. The system can be used to create virtual environments by optogenetic activation of sensory neurons, or to image activity in identified neurons at high magnification. By recording activity in neurons of freely moving C. elegans, we tested the long-standing hypothesis that forward and reverse locomotion are generated by distinct neuronal circuits. Surprisingly, we found motor neurons that are active during both types of locomotion, suggesting a new model of locomotion control in C. elegans. These results emphasize the importance of recording neuronal activity in freely moving animals and significantly expand the potential of imaging techniques by providing a mean to stabilize fluorescent targets.

在无束缚自由活动动物中开展无创神经元活动记录，无疑是神经元功能分析领域的终极目标之一，但此类记录技术至今仍难以实现。为解决这一核心难题，我们研发了一套可实时追踪神经元尺度荧光标记靶点的系统。该系统既可通过光遗传学（optogenetic）激活感觉神经元以构建虚拟环境，也可在高放大倍率下对已鉴定神经元的活动进行精准成像。通过对自由移动的秀丽隐杆线虫（C. elegans）的神经元活动进行记录，我们验证了一项长期存在的经典假说：秀丽隐杆线虫的正向与反向运动由各自独立的神经元环路调控产生。令人意外的是，我们发现了在两种运动模式下均被激活的运动神经元，这提示秀丽隐杆线虫存在一种全新的运动调控模型。本研究结果凸显了在自由活动动物中记录神经元活动的重要性，并通过提供稳定荧光标记靶点的有效手段，大幅拓展了神经成像技术的应用潜力。