107 research outputs found
Simultaneous multiplane imaging with reverberation multiphoton microscopy
Multiphoton microscopy (MPM) has gained enormous popularity over the years for its capacity to provide high resolution images from deep within scattering samples1. However, MPM is generally based on single-point laser-focus scanning, which is intrinsically slow. While imaging speeds as fast as video rate have become routine for 2D planar imaging, such speeds have so far been unattainable for 3D volumetric imaging without severely compromising microscope performance. We demonstrate here 3D volumetric (multiplane) imaging at the same speed as 2D planar (single plane) imaging, with minimal compromise in performance. Specifically, multiple planes are acquired by near-instantaneous axial scanning while maintaining 3D micron-scale resolution. Our technique, called reverberation MPM, is well adapted for large-scale imaging in scattering media with low repetition-rate lasers, and can be implemented with conventional MPM as a simple add-on.Accepted manuscrip
Neuronal imaging with ultrahigh dynamic range multiphoton microscopy
Multiphoton microscopes are hampered by limited dynamic range, preventing weak sample features from being detected in the presence of strong features, or preventing the capture of unpredictable bursts in sample strength. We present a digital electronic add-on technique that vastly improves the dynamic range of a multiphoton microscope while limiting potential photodamage. The add-on provides real-time negative feedback to regulate the laser power delivered to the sample, and a log representation of the sample strength to accommodate ultrahigh dynamic range without loss of information. No microscope hardware modifications are required, making the technique readily compatible with commercial instruments. Benefits are shown in both structural and in-vivo functional mouse brain imaging applications.R21 EY027549 - NEI NIH HH
Single-shot 3D widefield fluorescence imaging with a computational miniature mesoscope
Fluorescence imaging is indispensable to biology and neuroscience. The need for largescale
imaging in freely behaving animals has further driven the development in miniaturized
microscopes (miniscopes). However, conventional microscopes / miniscopes are inherently
constrained by their limited space-bandwidth-product, shallow depth-of-field, and inability
to resolve 3D distributed emitters. Here, we present a Computational Miniature Mesoscope
(CM2) that overcomes these bottlenecks and enables single-shot 3D imaging across an 8 ×
7-mm2 field-of-view and 2.5-mm depth-of-field, achieving 7-μm lateral resolution and
better than 200-μm axial resolution. Notably, the CM2 has a compact lightweight design
that integrates a microlens array for imaging and an LED array for excitation in a single
platform. Its expanded imaging capability is enabled by computational imaging that
augments the optics by algorithms. We experimentally validate the mesoscopic 3D imaging
capability on volumetrically distributed fluorescent beads and fibers. We further quantify
the effects of bulk scattering and background fluorescence on phantom experiments.Accepted manuscrip
The Bruce effect: Representational stability and memory formation in the accessory olfactory bulb of the female mouse
In the Bruce effect, a mated female mouse becomes resistant to the pregnancy-blocking effect of the stud. Various lines of evidence suggest that this form of behavioral imprinting results from reduced sensitivity of the female's accessory olfactory bulb (AOB) to the stud's chemosignals. However, the AOB's combinatorial code implies that diminishing responses to one individual will distort representations of other stimuli. Here, we record extracellular responses of AOB neurons in mated and unmated female mice while presenting urine stimuli from the stud and from other sources. We find that, while initial sensory responses in the AOB (within a timescale required to guide social interactions) remain stable, responses to extended stimulation (as required for eliciting the pregnancy block) display selective attenuation of stud-responsive neurons. Such temporal disassociation could allow attenuation of slow-acting endocrine processes in a stimulus-specific manner without compromising ongoing representations that guide behavior
Robust single-shot 3D fluorescence imaging in scattering media with a simulator-trained neural network
Imaging through scattering is a pervasive and difficult problem in many
biological applications. The high background and the exponentially attenuated
target signals due to scattering fundamentally limits the imaging depth of
fluorescence microscopy. Light-field systems are favorable for high-speed
volumetric imaging, but the 2D-to-3D reconstruction is fundamentally ill-posed,
and scattering exacerbates the condition of the inverse problem. Here, we
develop a scattering simulator that models low-contrast target signals buried
in heterogeneous strong background. We then train a deep neural network solely
on synthetic data to descatter and reconstruct a 3D volume from a single-shot
light-field measurement with low signal-to-background ratio (SBR). We apply
this network to our previously developed Computational Miniature Mesoscope and
demonstrate the robustness of our deep learning algorithm on scattering
phantoms with different scattering conditions. The network can robustly
reconstruct emitters in 3D with a 2D measurement of SBR as low as 1.05 and as
deep as a scattering length. We analyze fundamental tradeoffs based on network
design factors and out-of-distribution data that affect the deep learning
model's generalizability to real experimental data. Broadly, we believe that
our simulator-based deep learning approach can be applied to a wide range of
imaging through scattering techniques where experimental paired training data
is lacking
Rapid Changes in Synaptic Strength After Mild Traumatic Brain Injury
Traumatic brain injury (TBI) affects millions of Americans annually, but effective treatments remain inadequate due to our poor understanding of how injury impacts neural function. Data are particularly limited for mild, closed-skull TBI, which forms the majority of human cases, and for acute injury phases, when trauma effects and compensatory responses appear highly dynamic. Here we use a mouse model of mild TBI to characterize injury-induced synaptic dysfunction, and examine its progression over the hours to days after trauma. Mild injury consistently caused both locomotor deficits and localized neuroinflammation in piriform and entorhinal cortices, along with reduced olfactory discrimination ability. Using whole-cell recordings to characterize synaptic input onto piriform pyramidal neurons, we found moderate effects on excitatory or inhibitory synaptic function at 48 h after TBI and robust increase in excitatory inputs in slices prepared 1 h after injury. Excitatory increases predominated over inhibitory effects, suggesting that loss of excitatory-inhibitory balance is a common feature of both mild and severe TBI. Our data indicate that mild injury drives rapidly evolving alterations in neural function in the hours following injury, highlighting the need to better characterize the interplay between the primary trauma responses and compensatory effects during this early time period
Body mass index, muscle strength and physical performance in older adults from eight cohort studies: the HALCyon programme.
Objective
To investigate the associations of body mass index (BMI) and grip strength with objective measures of physical performance (chair rise time, walking speed and balance) including an assessment of sex differences and non-linearity.
Methods
Cross-sectional data from eight UK cohort studies (total N = 16 444) participating in the Healthy Ageing across the Life Course (HALCyon) research programme, ranging in age from 50 to 90+ years at the time of physical capability assessment, were used. Regression models were fitted within each study and meta-analysis methods used to pool regression coefficients across studies and to assess the extent of heterogeneity between studies.
Results
Higher BMI was associated with poorer performance on chair rise (N = 10 773), walking speed (N = 9 761) and standing balance (N = 13 921) tests. Higher BMI was associated with stronger grip strength in men only. Stronger grip strength was associated with better performance on all tests with a tendency for the associations to be stronger in women than men; for example, walking speed was higher by 0.43 cm/s (0.14, 0.71) more per kg in women than men. Both BMI and grip strength remained independently related with performance after mutual adjustment, but there was no evidence of effect modification. Both BMI and grip strength exhibited non-linear relations with performance; those in the lowest fifth of grip strength and highest fifth of BMI having particularly poor performance. Findings were similar when waist circumference was examined in place of BMI.
Conclusion
Older men and women with weak muscle strength and high BMI have considerably poorer performance than others and associations were observed even in the youngest cohort (age 53). Although causality cannot be inferred from observational cross-sectional studies, our findings suggest the likely benefit of early assessment and interventions to reduce fat mass and improve muscle strength in the prevention of future functional limitations
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