scholarly journals Emergent cortical circuit dynamics contain dense, interwoven ensembles of spike sequences

2017 ◽  
Vol 118 (3) ◽  
pp. 1914-1925 ◽  
Author(s):  
Joseph B. Dechery ◽  
Jason N. MacLean
Keyword(s):  
Ex Vivo ◽  
Temporal Coding ◽  
Population Activity ◽  
Flexible Assembly ◽  
Two Photon ◽  
Phase Sequence ◽  
Spike Sequences ◽  
Neuronal Assembly ◽  
Large Repertoire

Temporal codes are theoretically powerful encoding schemes, but their precise form in the neocortex remains unknown in part because of the large number of possible codes and the difficulty in disambiguating informative spikes from statistical noise. A biologically plausible and computationally powerful temporal coding scheme is the Hebbian assembly phase sequence (APS), which predicts reliable propagation of spikes between functionally related assemblies of neurons. Here, we sought to measure the inherent capacity of neocortical networks to produce reliable sequences of spikes, as would be predicted by an APS code. To record microcircuit activity, the scale at which computation is implemented, we used two-photon calcium imaging to densely sample spontaneous activity in murine neocortical networks ex vivo. We show that the population spike histogram is sufficient to produce a spatiotemporal progression of activity across the population. To more comprehensively evaluate the capacity for sequential spiking that cannot be explained by the overall population spiking, we identify statistically significant spike sequences. We found a large repertoire of sequence spikes that collectively comprise the majority of spiking in the circuit. Sequences manifest probabilistically and share neuron membership, resulting in unique ensembles of interwoven sequences characterizing individual spatiotemporal progressions of activity. Distillation of population dynamics into its constituent sequences provides a way to capture trial-to-trial variability and may prove to be a powerful decoding substrate in vivo. Informed by these data, we suggest that the Hebbian APS be reformulated as interwoven sequences with flexible assembly membership due to shared overlapping neurons. NEW & NOTEWORTHY Neocortical computation occurs largely within microcircuits comprised of individual neurons and their connections within small volumes (<500 μm3). We found evidence for a long-postulated temporal code, the Hebbian assembly phase sequence, by identifying repeated and co-occurring sequences of spikes. Variance in population activity across trials was explained in part by the ensemble of active sequences. The presence of interwoven sequences suggests that neuronal assembly structure can be variable and is determined by previous activity.

Endothelial glycocalyx thickness and platelet-vessel wall interactions during atherogenesis

2011 ◽  
Vol 106 (11) ◽  
pp. 939-946 ◽  
Author(s):  
Mirjam oude Egbrink ◽  
Viviane Heijnen ◽  
Remco Megens ◽  
Wim Engels ◽  
Hans Vink ◽  
...  
Keyword(s):  
Vessel Wall ◽  
Laser Scanning ◽  
Ex Vivo ◽  
Laser Scanning Microscopy ◽  
Endothelial Glycocalyx ◽  
Knock Out ◽  
Two Photon ◽  
Common Carotid Arteries ◽  
Wall Interactions

SummaryThe endothelial glycocalyx (EG), the luminal cover of endothelial cells, is considered to be atheroprotective. During atherogenesis, platelets adhere to the vessel wall, possibly triggered by simultaneous EG modulation. It was the objective of this study to investigate both EG thickness and platelet-vessel wall interactions during atherogenesis in the same experimental model. Intravital fluorescence microscopy was used to study platelet-vessel wall interactions in vivo in common carotid arteries and bifurcations of C57bl6/J (B6) and apolipoprotein E knock-out (ApoE-/-) mice (age 7 – 31 weeks). At the same locations, EG thickness was determined ex vivo using two-photon laser scanning microscopy. In ApoE-/- bifurcations the overall median level of adhesion was 48 platelets/mm2 (interquartile range: 16 – 80), which was significantly higher than in B6 bifurcations (0 (0 – 16), p = 0.001). This difference appeared to result from a significant age-dependent increase in ApoE-/- mice, while no such change was observed in B6 mice. At the same time, the EG in ApoE-/- bifurcations was significantly thinner than in B6 bifurcations (2.2 vs. 2.5 μm, respectively; p < 0.05). This resulted from the fact that in B6 bifurcations EG thickness increased with age (from 2.4 μm in young mice to 3.0 μm in aged ones), while in bifurcations of ApoE-/- mice this growth appeared to be absent (2.2 μm at all ages). During atherogenesis, platelet adhesion to the wall of the carotid artery bifurcation increases significantly. At the same location, EG growth with age is hampered. Therefore, glycocalyx-reinforcing strategies could possibly ameliorate atherosclerosis.

scholarly journals Ultrasound-assisted gatifloxacin delivery in mouse cornea, in vivo

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Uk Jegal ◽  
Jun Ho Lee ◽  
Jungbin Lee ◽  
Hyerin Jeong ◽  
Myoung Joon Kim ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Ophthalmic Solution ◽  
Ultrasound Treatment ◽  
Ocular Infection ◽  
Therapeutic Effects ◽  
Corneal Surface ◽  
Ultrasound Waves ◽  
Two Photon Microscopy ◽  
Two Photon

Abstract Gatifloxacin is a 4th generation fluoroquinolone antibiotic used in the clinic to treat ocular infection. One limitation of gatifloxacin is its relatively poor corneal penetration, and the increase of its trans-corneal delivery would be beneficial to reduce the amount or frequency of daily dose. In this study, ultrasound treatment was applied to enhance the trans-corneal delivery of gatifloxacin without damage. Experiments were conducted on mouse eyes in ex vivo and in vivo conditions. Ultrasound waves with 1 MHz in frequency, 1.3 W/cm2 in intensity were applied onto the mouse cornea for 5 minutes, and then gatifloxacin ophthalmic solution was instilled and left there for 10 minutes. 3D gatifloxacin distribution in the cornea was measured by two-photon microscopy (TPM) imaging based on its intrinsic fluorescence. Longitudinal TPM imaging of ultrasound treated mouse corneas showed the increase of initial gatifloxacin intensities on the corneal surface compared to untreated mouse corneas by 67%, and then the increased gatifloxacin delivery into the cornea from the surface at later time. The delivered gatifloxacin in the corneal epithelium stayed longer in the ultrasound treated corneas than in the untreated corneas. The enhanced trans-corneal delivery and extended stay of gatifloxacin in the mouse cornea by ultrasound treatment could be beneficial for therapeutic effects. This study demonstrated the detail process of enhanced trans-corneal gatifloxacin delivery by ultrasound treatment.

scholarly journals Two-Photon Microscopy Allows Imaging and Characterization of Cochlear Microvasculature In Vivo

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Friedrich Ihler ◽  
Mattis Bertlich ◽  
Bernhard Weiss ◽  
Steffen Dietzel ◽  
Martin Canis
Keyword(s):  
Fluorescence Microscopy ◽  
Inner Ear ◽  
Ex Vivo ◽  
Small Scale ◽  
Published Data ◽  
Cochlear Blood Flow ◽  
Two Photon ◽  
Two Photon Fluorescence ◽  
Photon Fluorescence

Impairment of cochlear blood flow has been discussed as factor in the pathophysiology of various inner ear disorders. However, the microscopic study of cochlear microcirculation is limited due to small scale and anatomical constraints. Here, two-photon fluorescence microscopy is applied to visualize cochlear microvessels. Guinea pigs were injected with Fluorescein isothiocyanate- or Texas red-dextrane as plasma marker. Intravital microscopy was performed in four animals and explanted cochleae from four animals were studied. The vascular architecture of the cochlea was visualized up to a depth of90.0±22.7 μm. Imaging yielded a mean contrast-to-noise ratio (CNR) of3.3±1.7. Mean diameter in vivo was16.5±6.0 μm for arterioles and8.0±2.4 μm for capillaries. In explanted cochleae, the diameter of radiating arterioles and capillaries was measured with12.2±1.6 μm and6.6±1.0 μm, respectively. The difference between capillaries and arterioles was statistically significant in both experimental setups (P<0.001andP=0.022, two-way ANOVA). Measured vessel diameters in vivo and ex vivo were in agreement with published data. We conclude that two-photon fluorescence microscopy allows the investigation of cochlear microvessels and is potentially a valuable tool for inner ear research.

scholarly journals Dual-color volumetric imaging of neural activity of cortical columns

2018 ◽  
Author(s):  
Shuting Han ◽  
Weijian Yang ◽  
Rafael Yuste
Keyword(s):  
Neural Activity ◽  
High Speed ◽  
Neural Circuits ◽  
Emergent Properties ◽  
Spatiotemporal Resolution ◽  
Population Activity ◽  
Volumetric Imaging ◽  
Two Photon ◽  
Dual Color

To capture the emergent properties of neural circuits, high-speed volumetric imaging of neural activity at cellular resolution is desirable. But while conventional two-photon calcium imaging is a powerful tool to study population activity in vivo, it is restrained to two-dimensional planes. Expanding it to 3D while maintaining high spatiotemporal resolution appears necessary. Here, we developed a two-photon microscope with dual-color laser excitation that can image neural activity in a 3D volume. We imaged the neuronal activity of primary visual cortex from awake mice, spanning from L2 to L5 with 10 planes, at a rate of 10 vol/sec, and demonstrated volumetric imaging of L1 long-range PFC projections and L2/3 somatas. Using this method, we map visually-evoked neuronal ensembles in 3D, finding a lack of columnar structure in orientation responses and revealing functional correlations between cortical layers which differ from trial to trial and are missed in sequential imaging. We also reveal functional interactions between presynaptic L1 axons and postsynaptic L2/3 neurons. Volumetric two-photon imaging appears an ideal method for functional connectomics of neural circuits.

scholarly journals Conditioning sharpens the spatial representation of rewarded stimuli in mouse primary visual cortex

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Pieter M Goltstein ◽  
Guido T Meijer ◽  
Cyriel MA Pennartz
Keyword(s):  
Visual Space ◽  
Spatial Separation ◽  
Time Lapse ◽  
Optical Signal ◽  
Population Coding ◽  
Cortical Representation ◽  
Population Activity ◽  
Two Photon ◽  
Structure Of Population

Reward is often employed as reinforcement in behavioral paradigms but it is unclear how the visuospatial aspect of a stimulus-reward association affects the cortical representation of visual space. Using a head-fixed paradigm, we conditioned mice to associate the same visual pattern in adjacent retinotopic regions with availability and absence of reward. Time-lapse intrinsic optical signal imaging under anesthesia showed that conditioning increased the spatial separation of mesoscale cortical representations of reward predicting- and non-reward predicting stimuli. Subsequent in vivo two-photon calcium imaging revealed that this improved separation correlated with enhanced population coding for retinotopic location, specifically for the trained orientation and spatially confined to the V1 region where rewarded and non-rewarded stimulus representations bordered. These results are corroborated by conditioning-induced differences in the correlation structure of population activity. Thus, the cortical representation of visual space is sharpened as consequence of associative stimulus-reward learning while the overall retinotopic map remains unaltered.

Two-Photon Imaging of Cellular Activities in Oxygen Sensing Tissues

2008 ◽  
Vol 14 (6) ◽  
pp. 519-525 ◽  
Author(s):  
Christoph Wotzlaw ◽  
Utta Berchner-Pfannschmidt ◽  
Joachim Fandrey ◽  
Helmut Acker
Keyword(s):  
Molecular Mechanisms ◽  
Ex Vivo ◽  
Oxygen Sensing ◽  
Rat Kidney ◽  
Hypoxia Inducible Factor ◽  
The Body ◽  
Cellular Functions ◽  
Protein Protein Interaction ◽  
Two Photon

AbstractThe cellular oxygen sensing system of the body ensures appropriate adaptation of cellular functions toward hypoxia by regulating gene expression and ion channel activity. Two-photon laser microscopy is an ideal tool to study and prove the relevance of the molecular mechanisms within oxygen sensing pathways on the cellular and complex tissue or organ level. Images of hypoxia inducible factor 1 (HIF-1) subunit nuclear mobility and protein-protein interaction in living cells, of hypoxia-induced changes in membrane potential and intracellular calcium of live ex vivo carotid bodies as well as of rat kidney proximal tubulus function in vivo, will be shown.

scholarly journals Calcium Imaging of Living Astrocytes in the Mouse Spinal Cord following Sensory Stimulation

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Giovanni Cirillo ◽  
Daniele De Luca ◽  
Michele Papa
Keyword(s):  
Spinal Cord ◽  
Cultured Cells ◽  
Ex Vivo ◽  
Sensory Stimulation ◽  
Widespread Application ◽  
Two Photon Microscopy ◽  
Two Photon ◽  
Heart Beating ◽  
Sensory Activity

Astrocytic Ca2+dynamics have been extensively studied inex vivomodels; however, the recent development of two-photon microscopy and astrocyte-specific labeling has allowed the study of Ca2+signaling in living central nervous system. Ca2+waves in astrocytes have been described in cultured cells and slice preparations, but evidence for astrocytic activation during sensory activity is lacking. There are currently few methods to image living spinal cord: breathing and heart-beating artifacts have impeded the widespread application of this technique. We here imaged the living spinal cord by two-photon microscopy in C57BL6/J mice. Through pressurized injection, we specifically loaded spinal astrocytes using the red fluorescent dye sulforhodamine 101 (SR101) and imaged astrocytic Ca2+levels with Oregon-Green BAPTA-1 (OGB). Then, we studied astrocytic Ca2+levels at rest and after right electrical hind paw stimulation. Sensory stimulation significantly increased astrocytic Ca2+levels within the superficial dorsal horn of the spinal cord compared to rest. In conclusion,in vivomorphofunctional imaging of living astrocytes in spinal cord revealed that astrocytes actively participate to sensory stimulation.

scholarly journals Deep tissue imaging by enhanced photon collection

2014 ◽  
Vol 07 (05) ◽  
pp. 1450034 ◽  
Author(s):  
Viera Crosignani ◽  
Sohail Jahid ◽  
Alexander Dvornikov ◽  
Enrico Gratton
Keyword(s):  
Ex Vivo ◽  
Second Harmonic ◽  
Fold Increase ◽  
Turbid Media ◽  
Tissue Imaging ◽  
Fluorescence Lifetime Imaging ◽  
Detection Scheme ◽  
Two Photon ◽  
Tissue Phantoms

We have developed a two-photon fluorescence microscope capable of imaging up to 4mm in turbid media with micron resolution. The key feature of this instrument is the innovative detector, capable of collecting emission photons from a wider surface area of the sample than detectors in traditional two-photon microscopes. This detection scheme is extremely efficient in the collection of emitted photons scattered by turbid media which allows eight fold increase in the imaging depth when compared with conventional two-photon microscopes. Furthermore, this system also has in-depth fluorescence lifetime imaging microscopy (FLIM) imaging capability which increases image contrast. The detection scheme captures emission light in a transmission configuration, making it extremely efficient for the detection of second harmonic generation (SHG) signals, which is generally forward propagating. Here we present imaging experiments of tissue phantoms and in vivo and ex vivo biological tissue performed with this microscope.

scholarly journals Bio-inspired microneedle design for efficient drug/vaccine coating

2019 ◽  
Vol 22 (1) ◽  
Author(s):  
Cristina Plamadeala ◽  
Saransh R. Gosain ◽  
Florian Hischen ◽  
Boris Buchroithner ◽  
Sujitha Puthukodan ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Biological Systems ◽  
Scientific Field ◽  
Skin Tests ◽  
Coating Process ◽  
Liquid Transport ◽  
True Bugs ◽  
Two Photon ◽  
Biomimetic Approach

AbstractBiomimetics is the interdisciplinary scientific field focused on the study and imitation of biological systems, with the aim of solving complex technological problems. In this paper, we present a new bio-inspired design for microneedles (MNs) and MN arrays, intended for rapidly coating the MNs with drug/vaccine. The biomimetic approach consists in ornamenting the lateral sides of pyramidal MNs with structures inspired by the external scent efferent systems of some European true bugs, which facilitate a directional liquid transport. To realize these MNs, two-photon polymerization (TPP) technique was used. Liquid coating capabilities of structured and non-structured MNs were compared. Moreover, both in-vivo and ex-vivo skin tests were performed to prove that MNs pierce the skin. We show that the arrays of MNs can be accurately replicated using a micro-moulding technique. We believe this design will be beneficial for the process of drug/vaccine loading onto the needles’ surfaces, by making it more efficient and by reducing the drug/vaccine wastage during MN coating process.

scholarly journals Imaging Collagen in Intact Viable Healthy and Atherosclerotic Arteries Using Fluorescently Labeled CNA35 and Two-Photon Laser Scanning Microscopy

2007 ◽  
Vol 6 (4) ◽  
pp. 7290.2007.00021 ◽  
Author(s):  
Remco T.A. Megens ◽  
Mirjam G.A. oude Egbrink ◽  
Jack P.M. Cleutjens ◽  
Marijke J.E. Kuijpers ◽  
Paul H.M. Schiffers ◽  
...  
Keyword(s):  
Molecular Imaging ◽  
Apolipoprotein E ◽  
Carotid Arteries ◽  
Ex Vivo ◽  
Atherosclerotic Plaques ◽  
Type I ◽  
Two Photon ◽  
Tunica Adventitia ◽  
Molecular Imaging Agent

We evaluated CNA35 as a collagen marker in healthy and atherosclerotic arteries of mice after both ex vivo and in vivo administration and as a molecular imaging agent for the detection of atherosclerosis. CNA35 conjugated with fluorescent Oregon Green 488 (CNA35/OG488) was administered ex vivo to mounted viable muscular (uterine), elastic (carotid), and atherosclerotic (carotid) arteries and fresh arterial rings. Two-photon microscopy was used for imaging. CNA35/OG488 labeling in healthy elastic arteries was compared with collagen type I, III, and IV antibody labeling in histologic sections. For in vivo labeling experiments, CNA35/OG488 was injected intravenously in C57BL6/J and apolipoprotein E−/− mice. Ex vivo CNA35/OG488 strongly labeled collagen in the tunica adventitia, media, and intima of muscular arteries. In healthy elastic arteries, tunica adventitia was strongly labeled, but labeling in tunica media and intima was prevented by endothelium and elastic laminae. Histology confirmed the affinity of CNA35 for type I, III, and IV collagen in arteries. Strong CNA35/OG488 labeling was found in atherosclerotic plaques. In vivo applied CNA35/OG488 minimally labeled the tunica intima of healthy carotid arteries. Atherosclerotic plaques in apolipoprotein E−/− mice exhibited large uptake. CNA35/OG488 imaging in organs revealed endothelium as a limiting barrier for in vivo uptake. CNA35/OG488 is a good molecular imaging agent for atherosclerosis.

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