The Gaussian mixture probability hypothesis density (GMPHD) filter is applied to the problem of tracking ground moving targets in clutter due to its excellent multitarget tracking performance, such ...as avoiding measurement-to-track association, and its easy implementation. For the existing GMPHD-based ground target tracking algorithm (the GMPHD filter incorporating map information using a coordinate transforming method, CT-GMPHD), the predicted probability density of its target state is given in road coordinates, while its target state update needs to be performed in Cartesian ground coordinates. Although the algorithm can improve the filtering performance to a certain extent, the coordinate transformation process increases the complexity of the algorithm and reduces its computational efficiency. To address this issue, this paper proposes two non-coordinate transformation roadmap fusion algorithms: directional process noise fusion (DNP-GMPHD) and state constraint fusion (SC-GMPHD). The simulation results show that, compared with the existing algorithms, the two proposed roadmap fusion algorithms are more accurate and efficient for target estimation performance on straight and curved roads in a cluttered environment. The proposed methods are additionally applied using a cardinalized PHD (CPHD) filter and a labeled multi-Bernoulli (LMB) filter. It is found that the PHD filter performs less well than the CPHD and LMB filters, but that it is also computationally cheaper.
Calcium imaging with protein-based indicators
is widely used to follow neural activity in intact nervous systems, but current protein sensors report neural activity at timescales much slower than ...electrical signalling and are limited by trade-offs between sensitivity and kinetics. Here we used large-scale screening and structure-guided mutagenesis to develop and optimize several fast and sensitive GCaMP-type indicators
. The resulting 'jGCaMP8' sensors, based on the calcium-binding protein calmodulin and a fragment of endothelial nitric oxide synthase, have ultra-fast kinetics (half-rise times of 2 ms) and the highest sensitivity for neural activity reported for a protein-based calcium sensor. jGCaMP8 sensors will allow tracking of large populations of neurons on timescales relevant to neural computation.
Genetically encoded voltage indicators (GEVIs) enable monitoring of neuronal activity at high spatial and temporal resolution. However, the utility of existing GEVIs has been limited by the ...brightness and photostability of fluorescent proteins and rhodopsins. We engineered a GEVI, called Voltron, that uses bright and photostable synthetic dyes instead of protein-based fluorophores, thereby extending the number of neurons imaged simultaneously in vivo by a factor of 10 and enabling imaging for significantly longer durations relative to existing GEVIs. We used Voltron for in vivo voltage imaging in mice, zebrafish, and fruit flies. In the mouse cortex, Voltron allowed single-trial recording of spikes and subthreshold voltage signals from dozens of neurons simultaneously over a 15-minute period of continuous imaging. In larval zebrafish, Voltron enabled the precise correlation of spike timing with behavior.
PIWI-interacting small RNAs (piRNAs) protect the germline genome and are essential for fertility. piRNAs originate from transposable element (TE) RNAs, long non-coding RNAs, or 3´ untranslated ...regions (3´UTRs) of protein-coding messenger genes, with the last being the least characterized of the three piRNA classes. Here, we demonstrate that the precursors of 3´UTR piRNAs are full-length mRNAs and that post-termination 80S ribosomes guide piRNA production on 3´UTRs in mice and chickens. At the pachytene stage, when other co-translational RNA surveillance pathways are sequestered, piRNA biogenesis degrades mRNAs right after pioneer rounds of translation and fine-tunes protein production from mRNAs. Although 3´UTR piRNA precursor mRNAs code for distinct proteins in mice and chickens, they all harbor embedded TEs and produce piRNAs that cleave TEs. Altogether, we discover a function of the piRNA pathway in fine-tuning protein production and reveal a conserved piRNA biogenesis mechanism that recognizes translating RNAs in amniotes.
In this paper, a model developed for establishing the lowest possible driving voltage of Holographic polymer-dispersed liquid crystal (H-PDLC) based on the Maxwell–Wagner effect doped with specific ...nanotubes. The dependences of the turning point frequency on the doping concentration and the distribution of multi-walled carbon nanotubes (MWCNTs) are discussed. The MWCNTs can effectively adjust the relaxation frequency of grating, increase its LC droplet size, and decrease its dielectric permittivity. The diffraction efficiency and threshold voltage of the prepared switchable Bragg grating were found to reach 91% and 0.77 V μm
−1
, respectively, at 5 kHz. By comparing the results of experiments and simulations, we obtained the mass distribution ratio of MWCNTs in the LC and polymer regions. It was found that the MWCNTs diffuse into the LC regions during the polymerization process, and the use of a suitable driving frequency and doping concentration can minimize the driving voltage. This work provides a reference for studying the dynamic range optical tuning and polymerization kinetics of nanoparticles in switchable gratings.
Abstract
Imaging membrane voltage from genetically defined cells offers the unique ability to report spatial and temporal dynamics of electrical signaling at cellular and circuit levels. Here, we ...present a general approach to engineer electrochromic fluorescence resonance energy transfer (eFRET) genetically encoded voltage indicators (GEVIs) with positive-going fluorescence response to membrane depolarization through rational manipulation of the native proton transport pathway in microbial rhodopsins. We transform the state-of-the-art eFRET GEVI Voltron into Positron, with kinetics and sensitivity equivalent to Voltron but flipped fluorescence signal polarity. We further apply this general approach to GEVIs containing different voltage sensitive rhodopsin domains and various fluorescent dye and fluorescent protein reporters.
The spinal substantia gelatinosa (SG; lamina II) is a major synaptic zone for unmyelinated (C) primary afferents. Whereas a substantial proportion of intrinsic SG neurones are GABAergic inhibitory, ...their relationship to afferent activity is unknown. In spinal cord slices from a transgenic mouse in which certain GABAergic lamina II neurones are labelled with green fluorescent protein (GFP), we compared primary afferent input with local efferent connections made by inhibitory SG neurones. Simultaneous whole‐cell recordings from characterized neurones establish that inhibitory SG neurones receive monosynaptic input from a subset of unmyelinated primary afferents and connect to other lamina II cells that have input from a different set of afferents, permitting interactions between distinctive afferent messages. Certain lamina II inhibitory cells were found to connect to one another by reciprocal links. Inhibitory lamina II connections appear arranged to modulate activity from different sets of peripheral unmyelinated fibres through neural circuitry that includes disinhibition.
The substantia gelatinosa (SG), a translucent layer of small nerve cells in the spinal cord's dorsal horn, is a major recipient of signals from thin, primary sensory fibres. Many SG neurons are inhibitory in function, but the mechanisms they serve are unknown. We found that in whole‐cell (intracellular) recordings from synaptically connected SG cells, the primary afferent input systematically differs. Connection patterns for particular types of neurones are repeatedly seen. The patterns established indicate that inhibitory cells form part of the circuitry producing programmed interactions between signals from different sensory information mediated by thin afferent fibres. The results document special inhibitory circuitry in the portion of the spinal cord that manages activity related to pain and temperature senses.
The ability to optically image cellular transmembrane voltages at millisecond-timescale resolutions can offer unprecedented insight into the function of living brains in behaving animals. Here, we ...present a point mutation that increases the sensitivity of Ace2 opsin-based voltage indicators. We use the mutation to develop Voltron2, an improved chemigeneic voltage indicator that has a 65% higher sensitivity to single APs and 3-fold higher sensitivity to subthreshold potentials than Voltron. Voltron2 retained the sub-millisecond kinetics and photostability of its predecessor, although with lower baseline fluorescence. In multiple in vitro and in vivo comparisons with its predecessor across multiple species, we found Voltron2 to be more sensitive to APs and subthreshold fluctuations. Finally, we used Voltron2 to study and evaluate the possible mechanisms of interneuron synchronization in the mouse hippocampus. Overall, we have discovered a generalizable mutation that significantly increases the sensitivity of Ace2 rhodopsin-based sensors, improving their voltage reporting capability.
•Voltron2 is an improved version of the chemigenetic voltage indicator Voltron•A point mutation enhances the sensitivity of several rhodopsin-based sensors•Voltron2 was tested in vivo in flies, fish, and mice
Abdelfattah et al. describe a point mutation that increases the sensitivity of voltage indicators. A new voltage indicator carrying that mutation (Voltron2) is found to have improved sensitivity over its predecessor. Voltron2 is validated in vivo and used to study the subthreshold activity of interneurons in the living mouse brain.
Most spinal cord injury (SCI) patients suffer from chronic pain. Effective therapy for this pain is lacking, and the underlying
mechanisms are poorly understood. The spinal superficial dorsal horn ...(SDH) contains neuronal circuits capable of modulating
primary afferent information involved in pain processing. KCC2 is an isoform of the K + âCl â cotransporter that contributes to the regulation of transmembrane anion gradient which plays a key role in shaping GABA A receptor-mediated signalling in the CNS. We tested the hypothesis that SCI causes down-regulation of KCC2 distal to the injury
and contributes to the neuronal hyperresponsiveness and pain-related behaviours. SCI was a hemisection at T 13 level of adult SpragueâDawley rats. Spinal sagittal slices with attached dorsal roots (DR) were prepared from L 4 to L 6 level. The reversal potentials of GABA responses ( E GABA ) and DR-evoked IPSPs and EPSPs of L 4-6 SDH neurones in sham-operated and SCI rats were compared using gramicidin-perforated patch-clamp recordings. Here we report
that thoracic SCI-induced down-regulation of KCC2 in the lumbar SDH parallels the development of allodynia. The subsequent
changes of E GABA in SDH neurones attenuate the GABA A receptor-mediated inhibitory synaptic transmission. These changes cause certain normally subthreshold primary A and C fibre
inputs to evoke action potential output in SDH neurones. We conclude that SCI induces KCC2 down-regulation and subsequent
changes of E GABA in the SDH below the injury site. The resulting disinhibition unmasks normally ineffective SDH neuronal circuits and may
contribute to the below-level central pain-related behaviours after incomplete SCI.
Mammalian cerebral cortex is accepted as being critical for voluntary motor control, but what functions depend on cortex is still unclear. Here we used rapid, reversible optogenetic inhibition to ...test the role of cortex during a head-fixed task in which mice reach, grab, and eat a food pellet. Sudden cortical inhibition blocked initiation or froze execution of this skilled prehension behavior, but left untrained forelimb movements unaffected. Unexpectedly, kinematically normal prehension occurred immediately after cortical inhibition, even during rest periods lacking cue and pellet. This 'rebound' prehension was only evoked in trained and food-deprived animals, suggesting that a motivation-gated motor engram sufficient to evoke prehension is activated at inhibition's end. These results demonstrate the necessity and sufficiency of cortical activity for enacting a learned skill.
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