![Wavelength‐dependent interaction between light and the brain. (a) Schematic of scattering and absorption of light in the tissue during in vivo imaging. (b) Reduced scattering and absorption of light with the increase in wavelength in the 400–1700 nm region. (a, b) Reproduced with permission. [14] Copyright 2021, Springer Nature Singapore Pvt Ltd. (c) The effective penetration depth of light with different wavelength in the brain. (d) The percentage of photons of light with different wavelength reaches a depth of 4 mm in the brain. (c, d) Reproduced with permission. [15] Copyright 2022, Oxford University Press on behalf of China Science Publishing & Media Ltd.](https://www.researchgate.net/publication/370565921/figure/fig2/AS:11431281244319359@1715891080992/Wavelength-dependent-interaction-between-light-and-the-brain-aSchematic-of-scattering_Q320.jpg)
![The NIR Ca²⁺ indicators. (a) Schematic diagram of NIR‐GECO1s and its mechanism of binding to Ca²⁺. The excitation and emission spectra of NIR‐GECOs in the presence and absence of Ca²⁺. Dashed lines represent the excitation spectrum, and solid lines represent the emission spectrum. (b) Traces of wide‐field imaging of Ca²⁺ with NIR‐GECO1s while neuronal activity is evoked. (a, b) Reproduced with permission. [38] Copyright 2019, Nature Publishing Group. (c) General view of iGECI and its response to Ca²⁺. Spectrum of iGECI in the absence (red line) and presence (black line) of Ca²⁺ measured in cell lysates of HEK293T cells. (d) Spontaneous Ca²⁺ monitoring with iGECI in cultured neurons. (c, d) Reproduced with permission. [40] Copyright 2021, Nature Publishing Group. (e) Schematic of HaloCaMP and its mechanism of response to Ca²⁺. HaloCaMP1a contains CaM‐binding peptides from myosin light chain kinase (MLCK), and HaloCaMP1b obtains CaM‐dependent kinase (CKK) to the N‐terminus. Spectrum of absorption (solid lines) and emission (dashed lines) of HaloCaMP1a‐JF635 in the absence and presence of Ca²⁺. (f) Ca²⁺ imaging of HaloCaMP1a and 1b labeled with different JF‐HTL to different numbers of APs. (e, f) Reproduced with permission. [41] Copyright 2021, Nature Publishing Group.](https://www.researchgate.net/publication/370565921/figure/fig3/AS:11431281244301141@1715891081179/The-NIR-Ca-indicators-aSchematic-diagram-of-NIR-GECO1s-and-its-mechanism-of-binding_Q320.jpg)
![Potassium indicators with K⁺‐selective filter micropores. (a) Schematic representation of K⁺ nanosensor based on UCNPs, and the selectivity and stability of K⁺ nanosensor. Reproduced with permission. [55] Copyright 2020, the American Association for the Advancement of Science. (b) Schematic design of the K⁺ nanosensor, and its selectivity of K⁺. Reproduced with permission. [57] Copyright 2020, Nature Publishing Group.](https://www.researchgate.net/publication/370565921/figure/fig4/AS:11431281244337586@1715891081441/Potassium-indicators-with-K-selective-filter-micropores-aSchematic-representation-of_Q320.jpg)
![ICG and Quasar monitor the membrane voltage in neurons. (a) ICG fluorescence is roughly linearly dependent on voltage. (b) ICG monitors a train of action potentials. (a, b) Reproduced with permission. [83] Copyright 2014, Elsevier Inc. (c) The constructs of co‐expression of CheRiff and QuasAr in the cell plasma membrane. CheRiff mediates blue light‐induced depolarization, and QuasAr monitors membrane voltage. Reproduced with permission. [74] Copyright 2014, Nature Publishing Group. (d) QuasAr3 monitors voltage alteration of neuronal activity in the hippocampus of a walking mouse. Reproduced with permission. [84] Copyright 2019, Nature Publishing Group.](https://www.researchgate.net/publication/370565921/figure/fig5/AS:11431281244319360@1715891081704/ICG-and-Quasar-monitor-the-membrane-voltage-in-neurons-aICG-fluorescence-is-roughly_Q320.jpg)
May 2023
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18 Citations
Almost all physiological processes of animals are controlled by the brain, including language, cognitive, memory, learning, emotion and so forth. Minor brain dysfunction usually leads to brain diseases and disorders. Therefore, it' is greatly meaningful and urgent for scientists to have a better understanding of brain structure and function. Optical approaches can provide powerful tools for imaging and modulating physiological processes of the brain. In particular, optical approaches in the near‐infrared (NIR) window (700–1700 nm) exhibit excellent prosperities of deep tissue penetration and low tissue scattering and absorption compared with those of visible windows (400–700 nm), which provides a promising approach for scientists to develop desired methods of neuroimaging and neuromodulation in deep brain tissues. In this review, variable types of NIR light approaches for imaging and modulating neural ions, membrane potential, neurotransmitters, and other critical molecules for brain functions and diseases are summarized. In particular, the latest breakthrough research of brain imaging and brain regulation in the NIR‐II window (1000–1700 nm) are highlighted. Finally, we conclude the challenges and prospects of NIR light‐based neuroimaging and neuromodulation for both basic brain research and further clinical translation.