A modern workhorse of neuroscience imaging is the two-photon microscope, which can stimulate a glow in cells labeled with a chemical called a fluorophore. Two photons with half the needed energy to stimulate the fluorophore arrive at the same time to make just a pinpointed cell glow, with less scattering and absorption by surrounding tissue than if one higher energy photon were sent barreling in.
Fly through the visual cortex
Fly through the visual cortex in this 3D video made by the Sur lab.
Mriganka Sur’s lab has been among those on the cutting edge of a new generation of advanced three-photon microscopy,having built one of the earliest scopes. The technology improves on two-photon scopes by penetrating even deeper, exposing more of the mammalian brain, in vivo, for exploration than ever before. Sur said his lab now has the capability to resolve cells well over a millimeter deep without the light damaging tissue. In Nature Communications in January 2019, the Sur Lab led by postoc Murat Yildirim demonstrated a series of important refinements that allowed them to image stimulated activity in all layers of the visual cortex in an awake mouse for the first time. Then in 2020, the lab published a study demonstrating that the technique allowed for making better associations between cortical brain structure and function..
Beginning in 2016 at the Society for Neuroscience Annual Meeting and at other conferences, Yildirim has also presented his three-photon work in combination with third harmonic generation microscopy , a method that doesn’t require labeling cells. THG resolves blood vessels and myelin white matter. He has also demonstrated the technology by imaging intact organoids derived from people with Rett syndrome.
