Multicolor multiscale brain imaging with chromatic multiphoton serial microscopy

Abstract

Large-scale microscopy approaches are transforming brain\xa0imaging, but currently lack efficient multicolor contrast modalities. We introduce chromatic multiphoton serial (ChroMS) microscopy, a method integrating one‐shot multicolor multiphoton excitation through wavelength mixing and serial block-face image acquisition. This approach provides organ-scale micrometric imaging of spectrally distinct fluorescent proteins and label-free nonlinear signals with constant micrometer-scale resolution and sub-micron channel registration over the entire imaged volume. We demonstrate tridimensional (3D) multicolor imaging over several cubic millimeters as well as brain-wide serial 2D multichannel imaging. We illustrate the strengths of this method through color-based 3D analysis of astrocyte morphology and contacts in the mouse cerebral cortex, tracing of individual pyramidal neurons\xa0within densely Brainbow-labeled tissue, and multiplexed whole-brain mapping of axonal projections labeled with spectrally distinct tracers. ChroMS will be an asset for multiscale and system-level studies in neuroscience and beyond.Multicolour images are difficult to acquire with large-scale microscopy approaches. Here the authors present a microtome-assisted microscope capable of trichromatic two-photon excitation and label-free nonlinear modalities based on wavelength mixing, and use it to analyze astrocyte morphology and neuronal projections in thick brain samples.