Hundreds Of Milliseconds Research Articles

A fast all-optical 3D photoacoustic scanner for clinical vascular imaging.

The clinical assessment of microvascular pathologies (in diabetes and in inflammatory skin diseases, for example) requires the visualization of superficial vascular anatomy. Photoacoustic tomography (PAT) scanners based on an all-optical Fabry-Perot ultrasound sensor can provide highly detailed 3D microvascular images, but minutes-long acquisition times have precluded their clinical use. Here we show that scan times can be reduced to a few seconds and even hundreds of milliseconds by parallelizing the optical architecture of the sensor readout, by using excitation lasers with high pulse-repetition frequencies and by exploiting compressed sensing. A PAT scanner with such fast acquisition minimizes motion-related artefacts and allows for the volumetric visualization of individual arterioles, venules, venous valves and millimetre-scale arteries and veins to depths approaching 15 mm, as well as for dynamic 3D images of time-varying tissue perfusion and other haemodynamic events. In exploratory case studies, we used the scanner to visualize and quantify microvascular changes associated with peripheral vascular disease, skin inflammation and rheumatoid arthritis. Fast all-optical PAT may prove useful in cardiovascular medicine, oncology, dermatology and rheumatology.

The eyes move towards fearful faces hundreds of milliseconds before they reach awareness

The eyes move towards fearful faces hundreds of milliseconds before they reach awareness

V2X Communication Computing Resource Collaboration Technology Based on Deep Reinforcement Learning

In traditional cloud computing, data needs to be transferred from distributed data sources to remote cloud data centers for high-performance computing. However, tasks often experience network transmission delays of hundreds of milliseconds or more from data sources to cloud data centers, which does not meet the need for low latency in V2X (Vehicle to Everything) systems. On the basis of the existing heterogeneous task scenario, this paper proposes a communication computing resource collaboration technology scheme based on heterogeneous task, which can meet the requirements of delay and cost when facing tasks with different delay requirements and different divisibility. This scheme uses the communication computing resources of the roadside unit and the service vehicle, so that the computing task of the task vehicle can be completed within the delay requirement and the cost is minimal. We use the deep reinforcement learning method to study, and finally the performance of the proposed scheme is verified by simulation.

Heterogeneity in Slow Synaptic Transmission Diversifies Purkinje Cell Timing.

The cerebellum plays an important role in diverse brain functions, ranging from motor learning to cognition. Recent studies have suggested that molecular and cellular heterogeneity within cerebellar lobules contributes to functional differences across the cerebellum. However, the specific relationship between molecular and cellular heterogeneity and diverse functional outputs of different regions of the cerebellum remains unclear. Here, we describe a previously unappreciated form of synaptic heterogeneity at parallel fiber synapses to Purkinje cells in the mouse cerebellum (both sexes). In contrast to uniform fast synaptic transmission, we found that the properties of slow synaptic transmission varied by up to threefold across different lobules of the mouse cerebellum, resulting in surprising heterogeneity. Depending on the location of a Purkinje cell, the time of peak of slow synaptic currents varied by hundreds of milliseconds. The duration and decay time of these currents also spanned hundreds of milliseconds, based on lobule. We found that, as a consequence of the heterogeneous synaptic dynamics, the same brief input stimulus was transformed into prolonged firing patterns over a range of timescales that depended on Purkinje cell location.

A distributed auditory network mediated by pontine central gray underlies ultra-fast awakening in response to alerting sounds

Sleeping animals can be woken up rapidly by external threat signals, which is an essential defense mechanism for survival. However, neuronal circuits underlying the fast transmission of sensory signals for this process remain unclear. Here, we report in mice that alerting sound can induce rapid awakening within hundreds of milliseconds and that glutamatergic neurons in the pontine central gray (PCG) play an important role in this process. These neurons exhibit higher sensitivity to auditory stimuli in sleep than wakefulness. Suppressing these neurons results in reduced sound-induced awakening and increased sleep in intrinsic sleep/wake cycles, whereas their activation induces ultra-fast awakening from sleep and accelerates awakening from anesthesia. Additionally, the sound-induced awakening can be attributed to the propagation of auditory signals from the PCG to multiple arousal-related regions, including the mediodorsal thalamus, lateral hypothalamus, and ventral tegmental area. Thus, the PCG serves as an essential distribution center to orchestrate a global auditory network to promote rapid awakening.

Proline substitutions in the ASIC1 β11-12 linker slow desensitization

Desensitization is a prominent feature of nearly all ligand-gated ion channels. Acid-sensing ion channels (ASICs) undergo desensitization within hundreds of milliseconds to seconds upon continual extracellular acidification. The ASIC mechanism of desensitization is primarily due to the isomerization or “flipping” of a short linker joining the 11th and 12th β sheets in the extracellular domain. In the resting and active states this β11-12 linker adopts an “upward” conformation while in the desensitized conformation the linker assumes a “downward” state. It is unclear if a single linker adopting the downward state is sufficient to desensitize the entire channel, or if all three are needed or some more complex scheme. To accommodate this downward state, specific peptide bonds within the linker adopt either trans-like or cis-like conformations. Since proline-containing peptide bonds undergo cis-trans isomerization very slowly, we hypothesized that introducing proline residues in the linker may slow or even abolish ASIC desensitization, potentially providing a valuable research tool. Proline substitutions in the chicken ASIC1 β11-12 linker (L414P and Y416P) slowed desensitization decays approximately 100- to 1000-fold as measured in excised patches. Both L414P and Y416P shifted the steady-state desensitization curves to more acidic pH values while activation curves and ion selectivity were largely unaffected (except for a left-shifted activation pH50 of L414P). To investigate the functional stoichiometry of desensitization in the trimeric ASIC, we created families of L414P and Y416P concatemers with zero, one, two, or three proline substitutions in all possible configurations. Introducing one or two L414P or Y416P substitutions only slightly attenuated desensitization, suggesting that conformational changes in the single remaining faster wild-type subunits were sufficient to desensitize the channel. These data highlight the unusual cis-trans isomerization mechanism of ASIC desensitization and support a model where ASIC desensitization requires only a single subunit.

MULTIPLE DISTINCT TIMESCALES OF RAPID SENSORY ADAPATION IN THE THALAMOCORTICAL CIRCUIT.

Numerous studies have shown that neuronal representations in sensory pathways are far from static but are instead strongly shaped by the complex properties of the sensory inputs they receive. Adaptation dynamically shapes the neural signaling that underlies our perception of the world yet remains poorly understood. We investigated rapid adaptation across timescales from hundreds of milliseconds to seconds through simultaneous multi-electrode recordings from the ventro-posteromedial nucleus of the thalamus (VPm) and layer 4 of the primary somatosensory cortex (S1) in male and female anesthetized mice in response to controlled, persistent whisker stimulation. Observations in VPm and S1 reveal a degree of adaptation that progresses through the pathway. Signatures of two distinct timescales of rapid adaptation in the firing rates of both thalamic and cortical neuronal populations were revealed, also reflected in the synchrony of the thalamic population and in the thalamocortical synaptic efficacy that was measured in putatively monosynaptically connected thalamocortical pairs. Controlled optogenetic activation of VPm further demonstrated that the longer timescale adaptation observed in S1 is likely inherited from slow decreases in thalamic firing rate and synchrony. Despite the degraded sensory responses, adaptation resulted in a shift in coding strategy that favors theoretical discrimination over detection across the observed timescales of adaptation. Overall, although multiple mechanisms contribute to rapid adaptation at distinct timescales, they support a unifying framework on the role of adaptation in sensory processing.

Insights into the Synaptic Properties of Dopamine Release Revealed by Single Walled Carbon Nanotube Biosensors

It is thought that there are two distinct modes of chemical neurotransmission, referred to as fast (synaptic) transmission and slow (volume) transmission. Fast transmission, mediated by ligand-gated ionotropic receptors, operate with millisecond temporal and nanometer spatial precision in excitatory and inhibitory synapses, primarily mediated by glutamate and GABA, respectively. In contrast, slow transmission relies on activation of G-protein coupled receptors (GPCRs) and is mediated by several classes of neuromodulators, including dopamine. Neuromodulators are thought to operate at temporal scales that range from hundreds of milliseconds to minutes, with a spatial specificity that is insufficiently understood but generally described as “diffuse”. In this work, we provide new evidence that shows the spatial precision of dopamine transmission is highly reminiscent of the spatial properties of signaling mediated by the fast acting neurotransmitters.To gain this insight, we used an optical assay named “DopaFilm” that is based on oligonucleotide functionalized single walled carbon nanotube dopamine sensors (nanosensors). Primary dopaminergic neurons were grown on top of glass coverslips functionalized with nanosensors, which enabled visualization of dopamine exocytosis events in single release sites under a continuous 785nm excitation laser. In axonal arbors, DopaFilm can report evoked and spontaneous dopamine release events with high signal to noise ratios of up to 50. Recording on DopaFilm revealed dopamine release is fast, calcium-dependent, and reliant on similar presynaptic protein machinery employed by fast neurotransmitters. These findings challenge the notion that dopamine is a slow transmitter; however it doesn’t preclude the possibility of imprecise spatial signaling, consistent with volume transmission theory. More recent data from our lab now challenges the spatial characteristics of volume transmission model as currently understood in the literature. In this talk, I will discuss new insights gained on dopamine signaling including clear examples of precise spatial arrangements of dopamine release sites, and ultrastructural, biochemical and spatial transcriptomic data that shows that neuromodulatory action can be highly spatially precise in nature.

Stereotyped spatiotemporal dynamics of spontaneous activity in visual cortex prior to eye-opening.

Over the course of development, functional sensory representations emerge in the visual cortex. Prior to eye-opening, modular patterns of spontaneous activity form long-range networks that may serve as a precursor for mature network organization. Although the spatial structure of these networks has been well studied, their temporal features, which may contribute to their continued plasticity and development, remain largely uncharacterized. To address this, we imaged hours of spontaneous network activity in the visual cortex of developing ferrets of both sexes utilizing a fast calcium indicator (GCaMP8m) and widefield imaging at high temporal resolution (50Hz), then segmented out spatiotemporal events. The spatial structure of this activity was highly modular, exhibiting spatially segregated active domains consistent with prior work. We found that the vast majority of events showed a clear dynamic component in which modules activated sequentially across the field of view, but only a minority of events were well-fit with a linear traveling wave. We found that spatiotemporal events occur in repeated and stereotyped motifs, reoccurring across hours of imaging. Finally, we found that the most frequently occurring single-frame spatial activity patterns were predictive of future activity patterns over hundreds of milliseconds. Together, our results demonstrate that spontaneous activity in the early developing cortex exhibits a rich spatiotemporal structure, suggesting a potential role in the maturation and refinement of future functional representations.

A dynamic scale-mixture model of motion in natural scenes.

Some of the most important tasks of visual and motor systems involve estimating the motion of objects and tracking them over time. Such systems evolved to meet the behavioral needs of the organism in its natural environment, and may therefore be adapted to the statistics of motion it is likely to encounter. By tracking the movement of individual points in movies of natural scenes, we begin to identify common properties of natural motion across scenes. As expected, objects in natural scenes move in a persistent fashion, with velocity correlations lasting hundreds of milliseconds. More subtly, but crucially, we find that the observed velocity distributions are heavy-tailed and can be modeled as a Gaussian scale-mixture. Extending this model to the time domain leads to a dynamic scale-mixture model, consisting of a Gaussian process multiplied by a positive scalar quantity with its own independent dynamics. Dynamic scaling of velocity arises naturally as a consequence of changes in object distance from the observer, and may approximate the effects of changes in other parameters governing the motion in a given scene. This modeling and estimation framework has implications for the neurobiology of sensory and motor systems, which need to cope with these fluctuations in scale in order to represent motion efficiently and drive fast and accurate tracking behavior.

Persistent Interruption in Parvalbumin-Positive Inhibitory Interneurons: Biophysical and Mathematical Mechanisms.

Persistent activity in excitatory pyramidal cells (PYRs) is a putative mechanism for maintaining memory traces during working memory. We have recently demonstrated persistent interruption of firing in fast-spiking parvalbumin-expressing interneurons (PV-INs), a phenomenon that could serve as a substrate for persistent activity in PYRs through disinhibition lasting hundreds of milliseconds. Here, we find that hippocampal CA1 PV-INs exhibit type 2 excitability, like striatal and neocortical PV-INs. Modeling and mathematical analysis showed that the slowly inactivating potassium current KV1 contributes to type 2 excitability, enables the multiple firing regimes observed experimentally in PV-INs, and provides a mechanism for robust persistent interruption of firing. Using a fast/slow separation of times scales approach with the KV1 inactivation variable as a bifurcation parameter shows that the initial inhibitory stimulus stops repetitive firing by moving the membrane potential trajectory onto a coexisting stable fixed point corresponding to a nonspiking quiescent state. As KV1 inactivation decays, the trajectory follows the branch of stable fixed points until it crosses a subcritical Hopf bifurcation (HB) and then spirals out into repetitive firing. In a model describing entorhinal cortical PV-INs without KV1, interruption of firing could be achieved by taking advantage of the bistability inherent in type 2 excitability based on a subcritical HB, but the interruption was not robust to noise. Persistent interruption of firing is therefore broadly applicable to PV-INs in different brain regions but is only made robust to noise in the presence of a slow variable, KV1 inactivation.

The method for identifying the potential of the fast response capability of a variable-speed pumped storage turbine in pump mode

Abstract Variable-speed pumped storage technology was being increasingly adopted by new power system to improve the operating and regulating characteristics of the hydropower unit and to stabilize the grid fluctuations. By connecting to a frequency converter, the variable-speed pumped storage unit can respond to grid fluctuations at a speed of hundreds of milliseconds. The fast response capability of a variable-speed pumped storage turbine should be considered in the design stage, be identified during the model test and be used as prerequisite during the commissioning stage of the unit. This article described the method for identifying the fast response capability and methods for improving the power regulation potential of a variable-speed pumped turbine in pump mode. The pipeline hydraulic loss, the guide vanes opening, the energy, cavitation and hump characteristics of the pump are the key parameters and should be carefully considered during the selection of the variable-speed operating zone.

Ultralong luminescence lifetime imaging of edible plant tissue for humidity sensing in food packaging by a smartphone

The safety of luminescence sensors and probes used in food packaging should be seriously considered, while most luminescence sensors were artificially synthesized with unclear toxicity, and cannot be directly used as indicators that were in contact with food. To overcome this problem, a humidity indicator based on an edible plant tissue was developed without any chemical processing. We found that garlic bulbs could emit significant persistent luminescence after drying at room temperature. The luminescence lifetime decreases from hundreds of milliseconds to tens of milliseconds as humidity increases. The long-lived luminescence could easily be detected through smartphones without any sophisticated instruments. The edible garlic is expected to be used as a humidity indicator in food packaging without worrying about food safety. Furthermore, the interference of scattered light and short-lived fluorescence from foods and packages can be eliminated in time-resolved luminescence imaging, greatly increasing the signal-to-noise ratio.

A Study on the Critical Saturation Response Characteristics of Simple and Sandwich Cylindrical Shells under Long-Duration Blast Loading.

Experimental research and numerical simulations of the structural response to shock waves with pulse durations of hundreds of milliseconds, or even seconds, are extremely challenging. This paper takes typical single-layer and sandwich cylindrical shells as the research objects. The response rules of cylindrical shells under long-duration blast loadings were studied. The results show that when the pulse duration is greater than or equal to 4~5 times the first-order period of the structure, the maximum response of the structure tends to be consistent, that is, the maximum response of the cylindrical shells with different vibration shapes shows a saturation effect as the pulse duration increases. This study established the relationship between the saturation loading time and the inherent characteristics of the structure. It was found that the saturation effect was applicable under the following conditions, including different load waveforms, elastic-plastic deformation of the structure, and the loading object being a sandwich shell. This will help transform the long-duration explosion wave problem into a finite pulse-duration shock wave problem that can be realized by both experiments and numerical simulations.

A Miniature Liquid Flowmeter Using All-Fiber Fabry–Perot Cavity for Real-Time Measurement

A miniature and highly sensitive fiber-optic liquid flowmeter based on Fabry–Perot interferometry (FPI) is proposed and demonstrated for fluid-flow micro-channel testing. The diaphragm deformation and pressure of the proposed sensor for flow rate detection are obtained from numerical and finite element method simulations of the theoretical model. The FPI flowmeter can be applied in real time to measure the ultra-wide dynamic range from 0 mL/min to 90 mL/min, with a response time of hundreds of milliseconds, controlling the flow rate with a resolution of 1.08 mL/min, which is 1.2% of the full scale. The quadratic functional relation between dip wavelength shifts and flow rates is verified by the flow calibration curves of the FPI flowmeter under dynamic pressure conditions. In addition, the effective temperature compensation is realized by connecting an FBG temperature sensor for variable temperature flow detection, and the measured error is reduced by nearly 25-times. The proposed sensor has the potential to measure the liquid flow rate in various applications.

Visual modulation of auditory evoked potentials in the cat

Visual modulation of the auditory system is not only a neural substrate for multisensory processing, but also serves as a backup input underlying cross-modal plasticity in deaf individuals. Event-related potential (ERP) studies in humans have provided evidence of a multiple-stage audiovisual interactions, ranging from tens to hundreds of milliseconds after the presentation of stimuli. However, it is still unknown if the temporal course of visual modulation in the auditory ERPs can be characterized in animal models. EEG signals were recorded in sedated cats from subdermal needle electrodes. The auditory stimuli (clicks) and visual stimuli (flashes) were timed by two independent Poison processes and were presented either simultaneously or alone. The visual-only ERPs were subtracted from audiovisual ERPs before being compared to the auditory-only ERPs. N1 amplitude showed a trend of transiting from suppression-to-facilitation with a disruption at ~ 100-ms flash-to-click delay. We concluded that visual modulation as a function of SOA with extended range is more complex than previously characterized with short SOAs and its periodic pattern can be interpreted with “phase resetting” hypothesis.

Functional magnetic resonance imaging signal has sub-second temporal accuracy

Neuronal activation sequence information is essential for understanding brain functions. Extracting such timing information from blood-oxygenation-level-dependent functional magnetic resonance imaging (fMRI) signals is confounded by local cerebral vascular reactivity (CVR), which varies across brain locations. Thus, detecting neuronal synchrony as well as inferring inter-regional causal modulation using fMRI signals can be biased. Here we used fast fMRI measurements sampled at 10 Hz to measure the fMRI latency difference between visual and sensorimotor areas when participants engaged in a visuomotor task. The regional fMRI timing was calibrated by subtracting the CVR latency measured by a breath-holding task. After CVR calibration, the fMRI signal at the lateral geniculate nucleus (LGN) preceded that at the visual cortex by 496 ms, followed by the fMRI signal at the sensorimotor cortex with a latency of 464 ms. Sequential LGN, visual, and sensorimotor cortex activations were found in each participant after the CVR calibration. These inter-regional fMRI timing differences across and within participants were more closely related to the reaction time after the CVR calibration. Our results suggested the feasibility of mapping brain activity using fMRI with accuracy in hundreds of milliseconds.

Tandem neural network-assisted inverse design of highly efficient diffractive slanted waveguide grating.

Virtual reality devices featuring diffractive grating components have emerged as hotspots in the field of near-to-eye displays. The core aim of our work is to streamline the intricacies involved in devising the highly efficient slanted waveguide grating using the deep-learning-driven inverse design technique. We propose and establish a tandem neural network (TNN) comprising a generative flow-based invertible neural network and a fully connected neural network. The proposed TNN can automatically optimize the coupling efficiencies of the proposed grating at multi-wavelengths, including red, green, and blue beams at incident angles in the range of 0°-15°. The efficiency indicators manifest in the peak transmittance, average transmittance, and illuminance uniformity, reaching approximately 100%, 92%, and 98%, respectively. Additionally, the structural parameters of the grating can be deduced inversely based on the indicators within a short duration of hundreds of milliseconds to seconds using the TNN. The implementation of the inverse-engineered grating is anticipated to serve as a paradigm for simplifying and expediting the development of diverse types of waveguide gratings.

Loading atoms from a large magnetic trap to a small intra-cavity optical lattice

We show that an optimized loading of a cold ensemble of rubidium-87 atoms from a magnetic trap into an optical lattice sustained by a single, far-red-detuned mode of a high-Q optical cavity can be efficient despite the large volume mismatch of the traps. The magnetically trapped atoms are magnetically transported to the vicinity of the cavity mode and released from the magnetic trap in a controlled way meanwhile undergoing an evaporation period. Large number of atoms get trapped in the dipole potential of the cavity mode for several hundreds of milliseconds. We monitor the number of atoms in the mode volume by a second tone of the cavity close to the atomic resonance. While this probe tone can pump atoms to another ground state uncoupled to the probe, we demonstrate state-independent trapping by applying a repumper laser.

Optically tunable mode-locked fiber laser using long-period grating coated with multiwall carbon nanotubes

We demonstrate an optically tunable mode-locked fiber laser using long-period fiber grating (LPFG) coated with multi-walled carbon nanotubes (CNTs). The multi-walled CNTs can absorb light to convert it into thermal energy, and the resonance wavelength of the grating can be easily turned by varying the external modulated light power. This multi-walled CNT coated LPFG-based all-optical fast and efficient spectrum tunable filter enables continuous tuning of the central wavelength of the laser by manipulating the loss of the mode-locked laser, ensuring the stability of the mode-locking state. In the absence of modulated light on multi-walled CNTs, the soliton laser could generate 890 fs pulses at 1546.7 nm with a spectrum bandwidth of 3.26 nm and a signal-to-noise ratio of 73.1 dB. Through adjustment of the pump power of the modulation light on multi-walled CNTs, the mode-locked fiber laser can be continuously tuned from 1546.71 to 1563.15 nm. The response time of the optically tunable system was measured to be in the order of hundreds of milliseconds. The presented optical tuning filter shows great potential in the fiber laser system, offering a repeatable, straightforward, and rapidly responsive laser tuning technique.