Accurately capturing the dynamic changes in neuronal and synaptic activity in the brain is one of the core challenges in neuroscience research. The new generation of multi-color miniaturized two-photon microscope independently developed by Chinese scientists recently weighs only 2.6 grams and achieves high-resolution deep brain two-photon color imaging of freely moving mice for the first time, providing a new tool for decoding complex brain functional mechanisms. This research and development result, which took 4 years, was published online on the 21st in the international academic journal Nature Methods. Two photon microscopy imaging technology is a nonlinear optical imaging technique based on two-photon absorption and excitation fluorescence, and one of its key components is a hollow fiber. People use the microstructure inside optical fibers to confine laser for transmission, and then hit cells labeled with fluorescence to generate fluorescent images. The imaging colors of lasers with different wavelengths are different. Previously, hollow fibers could only transmit ultrafast lasers of a single wavelength, limiting their multi-color imaging capabilities. The team led by Cheng Heping and Wang Aimin from Peking University, together with the team led by Wu Runlong from Beijing University of Information Science and Technology, has independently developed a new type of ultra wideband hollow fiber, which has the characteristics of low loss and low dispersion. It can achieve femtosecond pulse laser transmission at multiple wavelengths ranging from 700 to 1060 nanometers, and thus develop a multi-color miniaturized two-photon microscope. This is equivalent to live streaming the dynamic activity of neurons and organelles in color to the brain. ”Wu Runlong said that in the past, due to the limitations of hollow fiber optic functions, only single type cells could be observed under a microscope. Now, different types of cells can be labeled with different colors of fluorescence, allowing for clear visualization of complex behaviors between multiple cells and studying how they interact synergistically. Researchers put this microscope on the heads of mice with Alzheimer's disease and for the first time simultaneously captured dynamic images of neuronal calcium signals, mitochondrial calcium signals, and plaque deposition in red, green, and blue colors. They also observed abnormal cell and mitochondrial activity in adjacent plaques in the early stages of the disease. The team also obtained neuronal calcium signals and structural imaging in the cortex of mice at a depth of over 820 micrometers - the deepest known miniaturized two-photon microscopy imaging obtained without damaging brain tissue. In addition, the microscope lens has successfully achieved a seamless transition between large field of view observation and high-resolution fine imaging. Cheng Heping, director of the National Biomedical Imaging Science Center of Peking University and an academician of the CAS Member, said that for many years, the ability of noninvasive deep brain imaging with multi-color fluorescent markers could only be realized on large desktop devices. The team solved the problem of multi-color excitation imaging with a miniature two-photon microscope for the first time, bringing breakthrough progress to the research of complex brain networks. In the future, this technology will have broad application prospects in understanding the principles of brain cognition, studying the mechanisms of brain diseases, evaluating neuropharmaceuticals, and brain computer interfaces. (New Society)