In vivo three-photon microscopy of subcortical structures within an intact mouse brain
TL;DR: Non-invasive, high-resolution, in vivo imaging of subcortical structures (the external capsule and hippocampus) within an intact mouse brain is demonstrated using three-photon fluorescence microscopy at the new spectral window of 1700 nm.
Abstract: Two-photon fluorescence microscopy (2PM)1 enables scientists in various fields including neuroscience2,3, embryology4, and oncology5 to visualize in vivo and ex vivo tissue morphology and physiology at a cellular level deep within scattering tissue. However, tissue scattering limits the maximum imaging depth of 2PM within the mouse brain to the cortical layer, and imaging subcortical structures currently requires the removal of overlying brain tissue3 or the insertion of optical probes6,7. Here we demonstrate non-invasive, high resolution, in vivo imaging of subcortical structures within an intact mouse brain using three-photon fluorescence microscopy (3PM) at a spectral excitation window of 1,700 nm. Vascular structures as well as red fluorescent protein (RFP)-labeled neurons within the mouse hippocampus are imaged. The combination of the long excitation wavelength and the higher order nonlinear excitation overcomes the limitations of 2PM, enabling biological investigations to take place at greater depth within tissue.
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TL;DR: This Review covers recent progress on near-infrared fluorescence imaging for preclinical animal studies and clinical diagnostics and interventions.
Abstract: This Review covers recent progress on near-infrared fluorescence imaging for preclinical animal studies and clinical diagnostics and interventions.
1,774 citations
1,063 citations
TL;DR: Through-scalp and through-skull fluorescence imaging of mouse cerebral vasculature without craniotomy is reported utilizing the intrinsic photoluminescence of single-walled carbon nanotubes in the 1.3–1.4 micrometre near-infrared window, providing real-time assessment of blood flow anomaly in a mouse middle cerebral artery occlusion stroke model.
Abstract: To date, brain imaging has largely relied on X-ray computed tomography and magnetic resonance angiography with limited spatial resolution and long scanning times. Fluorescence-based brain imaging in the visible and traditional near-infrared regions (400-900 nm) is an alternative but currently requires craniotomy, cranial windows and skull thinning techniques, and the penetration depth is limited to 1-2 mm due to light scattering. Here, we report through-scalp and through-skull fluorescence imaging of mouse cerebral vasculature without craniotomy utilizing the intrinsic photoluminescence of single-walled carbon nanotubes in the 1.3-1.4 micrometre near-infrared window. Reduced photon scattering in this spectral region allows fluorescence imaging reaching a depth of >2 mm in mouse brain with sub-10 micrometre resolution. An imaging rate of ~5.3 frames/s allows for dynamic recording of blood perfusion in the cerebral vessels with sufficient temporal resolution, providing real-time assessment of blood flow anomaly in a mouse middle cerebral artery occlusion stroke model.
781 citations
TL;DR: Improved red GECIs based on mRuby (jRCaMP1a, b) and mApple (jRGECO1a) are presented, with sensitivity comparable to GCaMP6, to facilitate deep-tissue imaging, dual-color imaging together with GFP-based reporters, and the use of optogenetics in combination with calcium imaging.
Abstract: Neurons encode information with brief electrical pulses called spikes. Monitoring spikes in large populations of neurons is a powerful method for studying how networks of neurons process information and produce behavior. This activity can be detected using fluorescent protein indicators, or “probes”, which light up when neurons are active. The best existing probes produce green fluorescence. However, red fluorescent probes would allow us to see deeper into the brain, and could also be used with green probes to image the activity and interactions of different neuron types simultaneously. However, existing red fluorescent probes are not as good at detecting neural activity as green probes. By optimizing two existing red fluorescent proteins, Dana et al. have now produced two new red fluorescent probes, each with different advantages. The new protein indicators detect neural activity with high sensitivity and allow researchers to image previously unseen brain activity. Tests showed that the probes work in cultured neurons and allow imaging of the activity of neurons in mice, flies, fish and worms. History has shown that enhancing the techniques used to study biological processes can lead to fundamentally new insights. In the future, Dana et al. would therefore like to make even more sensitive protein indicators that will allow larger networks of neurons deeper in the brain to be imaged.
762 citations
Cites background from "In vivo three-photon microscopy of ..."
...Imaging with red probes suffers less from scattering of excitation light and absorption of fluorescence compared with GFP-based sensors (Figure 2—figure supplement 1), which could allow deeper imaging in vivo (Horton et al., 2013)....
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...We report on the mRuby-based jRCaMP1a and jRCaMP1b, and mApple-based jRGECO1a, all of which show severalfold improved sensitivity for detecting neural activity compared to their parent scaffolds....
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TL;DR: A new 3D microscopy technique that allows volumetric imaging of living samples at ultra-high speeds: Swept, confocally-aligned planar excitation (SCAPE) microscopy, demonstrated by imaging spontaneous neuronal firing in the intact brain of awake behaving mice, as well as freely moving transgenic Drosophila larvae.
Abstract: We report a new 3D microscopy technique that allows volumetric imaging of living samples at ultra-high speeds: Swept, confocally-aligned planar excitation (SCAPE) microscopy. While confocal and two-photon microscopy have revolutionized biomedical research, current implementations are costly, complex and limited in their ability to image 3D volumes at high speeds. Light-sheet microscopy techniques using two-objective, orthogonal illumination and detection require a highly constrained sample geometry, and either physical sample translation or complex synchronization of illumination and detection planes. In contrast, SCAPE microscopy acquires images using an angled, swept light-sheet in a single-objective, en-face geometry. Unique confocal descanning and image rotation optics map this moving plane onto a stationary high-speed camera, permitting completely translationless 3D imaging of intact samples at rates exceeding 20 volumes per second. We demonstrate SCAPE microscopy by imaging spontaneous neuronal firing in the intact brain of awake behaving mice, as well as freely moving transgenic Drosophila larvae.
513 citations
References
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31 Jul 2001
TL;DR: The 3rd edition of this atlas is now in more practical 14"x11" format for convenient lab use and includes a CD of all plates and diagrams, as well as Adobe Illustrator files of the diagrams, and a variety of additional useful material.
Abstract: "The Mouse Brain in Stereotaxic Coordinates" is the most widely used and cited atlas of the mouse brain in print. It provides researchers and students with both accurate stereotaxic coordinates for laboratory use, and detailed delineations and indexing of structures for reference. The accompanying DVD provides drawings of brains structures that can be used as templates for making figures for publication. The 3rd edition is both a major revision and an expansion of previous editions. Delineations and photographs in the horizontal plane of section now complement the coronal and sagittal series, and all the tissue sections are now shown in high resolution digital color photography. The photographs of the sections and the intermediate sections are also provided on the accompanying DVD in high-resolution JP 2000 format. The delineations of structures have been revised, and naming conventions made consistent with Paxinos and Watson's "Rat Brain in Stereotaxic Coordinates, 6th Edition". The 3rd edition of this atlas is now in more practical 14"x11" format for convenient lab use. This edition is in full color throughout. It includes a CD of all plates and diagrams, as well as Adobe Illustrator files of the diagrams, and a variety of additional useful material. Coronal and sagittal diagrams are completely reworked and updated. Rhombomeric borders are included in sagittal figures, for the first time in mammals. Microscopic plates are scanned with a new method in much higher quality.
15,681 citations
TL;DR: The fluorescence emission increased quadratically with the excitation intensity so that fluorescence and photo-bleaching were confined to the vicinity of the focal plane as expected for cooperative two-photon excitation.
Abstract: Molecular excitation by the simultaneous absorption of two photons provides intrinsic three-dimensional resolution in laser scanning fluorescence microscopy. The excitation of fluorophores having single-photon absorption in the ultraviolet with a stream of strongly focused subpicosecond pulses of red laser light has made possible fluorescence images of living cells and other microscopic objects. The fluorescence emission increased quadratically with the excitation intensity so that fluorescence and photo-bleaching were confined to the vicinity of the focal plane as expected for cooperative two-photon excitation. This technique also provides unprecedented capabilities for three-dimensional, spatially resolved photochemistry, particularly photolytic release of caged effector molecules.
8,905 citations
TL;DR: Fundamental concepts of nonlinear microscopy are reviewed and conditions relevant for achieving large imaging depths in intact tissue are discussed.
Abstract: With few exceptions biological tissues strongly scatter light, making high-resolution deep imaging impossible for traditional⎯including confocal⎯fluorescence microscopy. Nonlinear optical microscopy, in particular two photon–excited fluorescence microscopy, has overcome this limitation, providing large depth penetration mainly because even multiply scattered signal photons can be assigned to their origin as the result of localized nonlinear signal generation. Two-photon microscopy thus allows cellular imaging several hundred microns deep in various organs of living animals. Here we review fundamental concepts of nonlinear microscopy and discuss conditions relevant for achieving large imaging depths in intact tissue.
3,781 citations
TL;DR: In this paper, the two-photon fluorescence excitation (TPE) spectra were measured for 11 common molecular fluorophores in the excitation wavelength range 690 nm < λ < 1050 nm.
Abstract: Measurements of two-photon fluorescence excitation (TPE) spectra are presented for 11 common molecular fluorophores in the excitation wavelength range 690 nm < λ < 1050 nm. Results of excitation by ∼100-fs pulses of a mode-locked Ti:sapphire laser are corroborated by single-mode cw Ti:sapphire excitation data in the range 710 nm < λ < 840 nm. Absolute values of the TPE cross section for Rhodamine B and Fluorescein are obtained by comparison with one-photon-excited fluorescence, assuming equal emission quantum efficiencies. TPE action cross sections for the other nine fluorophores are also determined. No differences between one-photon- and two-photon-excited fluorescence emission spectra are found. TPE emission spectra are independent of excitation wavelength. With both pulsed and cw excitation the fluorescence emission intensities are strictly proportional to the square of the excitation intensity to within ±4% for excitation intensities sufficiently below excited-state saturation.
2,140 citations
"In vivo three-photon microscopy of ..." refers background in this paper
...5CC3nn0 (NNNN)2<PP>3 ππ3 ee −3zz llee , (2) where NNNN is the numerical aperture of the focusing lens, nn0 is the index of refraction of the imaging medium, < PP > is the time-averaged power of the excitation beam, λλ is the excitation wavelength, and zz is the imaging depth in the tissue....
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TL;DR: Strategies to visualize synaptic circuits by genetically labelling neurons with multiple, distinct colours are presented and may facilitate the analysis of neuronal circuitry on a large scale.
Abstract: Detailed analysis of neuronal network architecture requires the development of new methods. Here we present strategies to visualize synaptic circuits by genetically labelling neurons with multiple, distinct colours. In Brainbow transgenes, Cre/lox recombination is used to create a stochastic choice of expression between three or more fluorescent proteins (XFPs). Integration of tandem Brainbow copies in transgenic mice yielded combinatorial XFP expression, and thus many colours, thereby providing a way to distinguish adjacent neurons and visualize other cellular interactions. As a demonstration, we reconstructed hundreds of neighbouring axons and multiple synaptic contacts in one small volume of a cerebellar lobe exhibiting approximately 90 colours. The expression in some lines also allowed us to map glial territories and follow glial cells and neurons over time in vivo. The ability of the Brainbow system to label uniquely many individual cells within a population may facilitate the analysis of neuronal circuitry on a large scale.
1,746 citations