All-Optical Physiology for Neural-Circuitry Analysis

Significance The brain program, which focuses strategically on neuroscience research, has been launched worldwide. The construction of neural connection maps is the basis of neuroscience research. Meanwhile, the analysis of neural circuits can provide a basis for investigations into the mechanisms of perception, memory, and social behavior, as well as the diagnosis and treatment of related diseases. Additionally, relevant investigations can inspire the development of next-generation artificial-intelligence algorithms and promote the development of the intelligent information industry. Progress The development of optical technology and functional proteins in recent years has enabled scientists to use fluorescence imaging technology based on functional indicator proteins to observe neural activity, as well as use optogenetics based on opsins to regulate neural activity. All-optical physiology combines the observation and regulation of neural activity based on optical technology, which offers the advantages of low invasibility, high spatial resolution, and high throughput compared with conventional electrophysiological techniques, and has become an ideal method for the analysis of neural functional circuits in vivo. In this paper, the technical route of all-optical physiological technology is first introduced (Fig. 1). In the second section, the principles and characteristics of the functional indicators of fluorescent and photosensitive proteins are introduced (Fig. 2). third section, the basic optical-path structure and technical realization method of all-optical physiological systems are reviewed (Fig. 3), and typical results based on single- and two-photon imaging are shown (Fig. 4). In the fourth section, the performance-evaluation Indexes of all-optical physiological systems in the time and space dimensions are analyzed (Fig. 5), and recent improvements for enhancing the system performance are presented (Fig. 6). Conclusions and Prospects The main research tools used in neuroscience have shifted from electrical to optical devices. All-optical physiological systems have been improved gradually. Integrating advanced technologies in the field of imaging and optogenetics enables the development of a mesoscopic multiphoton all-optical physiological system that can realize high-speed and accurate observations and regulations of hundreds of neurons in the entire brain region or several brain regions in three-dimensional space, analyze neural functional circuits, and construct a brain functional connection map.