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195 Janelia Publications

Showing 81-90 of 195 results
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    08/13/15 | Lighting up genes in single cells at scale.
    Liu Z
    Cell. 2015 Aug 13;162(4):705-7. doi: 10.1016/j.cell.2015.07.052
    08/11/15 | Whole-central nervous system functional imaging in larval Drosophila.
    Lemon WC, Pulver SR, Höckendorf B, McDole K, Branson KM, Freeman J, Keller PJ
    Nature Communications. 2015 Aug 11;6:7924. doi: 10.1038/ncomms8924

    Understanding how the brain works in tight concert with the rest of the central nervous system (CNS) hinges upon knowledge of coordinated activity patterns across the whole CNS. We present a method for measuring activity in an entire, non-transparent CNS with high spatiotemporal resolution. We combine a light-sheet microscope capable of simultaneous multi-view imaging at volumetric speeds 25-fold faster than the state-of-the-art, a whole-CNS imaging assay for the isolated Drosophila larval CNS and a computational framework for analysing multi-view, whole-CNS calcium imaging data. We image both brain and ventral nerve cord, covering the entire CNS at 2 or 5 Hz with two- or one-photon excitation, respectively. By mapping network activity during fictive behaviours and quantitatively comparing high-resolution whole-CNS activity maps across individuals, we predict functional connections between CNS regions and reveal neurons in the brain that identify type and temporal state of motor programs executed in the ventral nerve cord.

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    Chklovskii LabFlyEM
    08/06/15 | Automatic adaptation to fast input changes in a time-invariant neural circuit.
    Bharioke A, Chklovskii DB
    PLoS Computational Biology. 2015 Aug 6;11(8):e1004315. doi: 10.1371/journal.pcbi.1004315
    Svoboda Lab
    08/06/15 | Low-noise encoding of active touch by layer 4 in the somatosensory cortex.
    Andrew Hires S, Gutnisky DA, Yu J, O'Connor DH, Svoboda K
    eLife. 2015 Aug 6;4:. doi: 10.7554/eLife.06619

    Cortical spike trains often appear noisy, with the timing and number of spikes varying across repetitions of stimuli. Spiking variability can arise from internal (behavioral state, unreliable neurons, or chaotic dynamics in neural circuits) and external (uncontrolled behavior or sensory stimuli) sources. The amount of irreducible internal noise in spike trains, an important constraint on models of cortical networks, has been difficult to estimate, since behavior and brain state must be precisely controlled or tracked. We recorded from excitatory barrel cortex neurons in layer 4 during active behavior, where mice control tactile input through learned whisker movements. Touch was the dominant sensorimotor feature, with >70% spikes occurring in millisecond timescale epochs after touch onset. The variance of touch responses was smaller than expected from Poisson processes, often reaching the theoretical minimum. Layer 4 spike trains thus reflect the millisecond-timescale structure of tactile input with little noise.

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    08/05/15 | Drosophila germ granules are structured and contain homotypic mRNA clusters.
    Trcek T, Grosch M, York A, Shroff H, Lionnet T, Lehmann R
    Nature Communications. 2015 Aug 5;6:7962. doi: 10.1038/ncomms8962

    Germ granules, specialized ribonucleoprotein particles, are a hallmark of all germ cells. In Drosophila, an estimated 200 mRNAs are enriched in the germ plasm, and some of these have important, often conserved roles in germ cell formation, specification, survival and migration. How mRNAs are spatially distributed within a germ granule and whether their position defines functional properties is unclear. Here we show, using single-molecule FISH and structured illumination microscopy, a super-resolution approach, that mRNAs are spatially organized within the granule whereas core germ plasm proteins are distributed evenly throughout the granule. Multiple copies of single mRNAs organize into 'homotypic clusters' that occupy defined positions within the center or periphery of the granule. This organization, which is maintained during embryogenesis and independent of the translational or degradation activity of mRNAs, reveals new regulatory mechanisms for germ plasm mRNAs that may be applicable to other mRNA granules.

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    Singer Lab
    08/01/15 | Single-molecule insights into mRNA dynamics in neurons.
    Buxbaum AR, Yoon YJ, Singer RH, Park HY
    Trends in Cell Biology. 2015 Aug;25(8):468-75. doi: 10.1016/j.tcb.2015.05.005

    Targeting of mRNAs to neuronal dendrites and axons plays an integral role in intracellular signaling, development, and synaptic plasticity. Single-molecule imaging of mRNAs in neurons and brain tissue has led to enhanced understanding of mRNA dynamics. Here we discuss aspects of mRNA regulation as revealed by single-molecule detection, which has led to quantitative analyses of mRNA diversity, localization, transport, and translation. These exciting new discoveries propel our understanding of the life of an mRNA in a neuron and how its activity is regulated at the single-molecule level.

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    Ji LabGENIE
    07/29/15 | Neuronal representation of ultraviolet visual stimuli in mouse primary visual cortex.
    Tan Z, Sun W, Chen T, Kim D, Ji N
    Scientific Reports. 2015 Jul 29;5:12597. doi: 10.1038/srep12597

    The mouse has become an important model for understanding the neural basis of visual perception. Although it has long been known that mouse lens transmits ultraviolet (UV) light and mouse opsins have absorption in the UV band, little is known about how UV visual information is processed in the mouse brain. Using a custom UV stimulation system and in vivo calcium imaging, we characterized the feature selectivity of layer 2/3 neurons in mouse primary visual cortex (V1). In adult mice, a comparable percentage of the neuronal population responds to UV and visible stimuli, with similar pattern selectivity and receptive field properties. In young mice, the orientation selectivity for UV stimuli increased steadily during development, but not direction selectivity. Our results suggest that, by expanding the spectral window through which the mouse can acquire visual information, UV sensitivity provides an important component for mouse vision.

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    07/22/15 | A specific component of the evoked potential mirrors phasic dopamine neuron activity during conditioning.
    Pan W, Dudman JT
    The Journal of Neuroscience : the official journal of the Society for Neuroscience. 2015 Jul 22;35(29):10451-9. doi: 10.1523/JNEUROSCI.4096-14.2015

    UNLABELLED: Midbrain dopamine (DA) neurons are thought to be a critical node in the circuitry that mediates reward learning. DA neurons receive diverse inputs from regions distributed throughout the neuraxis from frontal neocortex to the mesencephalon. While a great deal is known about changes in the activity of individual DA neurons during learning, much less is known about the functional changes in the microcircuits in which DA neurons are embedded. Here we used local field potentials recorded from the midbrain of behaving mice to show that the midbrain evoked potential (mEP) faithfully reflects the temporal and spatial structure of the phasic response of midbrain neuron populations during conditioning. By comparing the mEP to simultaneously recorded single units, we identified specific components of the mEP that corresponded to phasic DA and non-DA responses to salient stimuli. The DA component of the mEP emerged with the acquisition of a conditioned stimulus, was extinguished following changes in reinforcement contingency, and could be inhibited by pharmacological manipulations that attenuate the phasic responses of DA neurons. In contrast to single-unit recordings, the mEP permitted relatively dense sampling of the midbrain circuit during conditioning and thus could be used to reveal the spatiotemporal structure of multiple intermingled midbrain circuits. Finally, the mEP response was stable for months and thus provides a new approach to study long-term changes in the organization of ventral midbrain microcircuits during learning.

    SIGNIFICANCE STATEMENT: Neurons that synthesize and release the neurotransmitter dopamine play a critical role in voluntary reward-seeking behavior. Much of our insight into the function of dopamine neurons comes from recordings of individual cells in behaving animals; however, it is notoriously difficult to record from dopamine neurons due to their sparsity and depth, as well as the presence of intermingled non-dopaminergic neurons. Here we show that much of the information that can be learned from recordings of individual dopamine and non-dopamine neurons is also revealed by changes in specific components of the local field potential. This technique provides an accessible measurement that could prove critical to our burgeoning understanding of the molecular, functional, and anatomical diversity of neuron populations in the midbrain.

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    Singer Lab
    07/20/15 | Inferring transient particle transport dynamics in live cells.
    Monnier N, Barry Z, Park HY, Su K, Katz Z, English BP, Dey A, Pan K, Cheeseman IM, Singer RH, Bathe M
    Nature Methods. 2015 Jul 20;12(9):838-40. doi: 10.1038/nmeth.3483

    Live-cell imaging and particle tracking provide rich information on mechanisms of intracellular transport. However, trajectory analysis procedures to infer complex transport dynamics involving stochastic switching between active transport and diffusive motion are lacking. We applied Bayesian model selection to hidden Markov modeling to infer transient transport states from trajectories of mRNA-protein complexes in live mouse hippocampal neurons and metaphase kinetochores in dividing human cells. The software is available at http://hmm-bayes.org/.

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    07/20/15 | Neuron hemilineages provide the functional ground plan for the Drosophila ventral nervous system.
    Harris RM, Pfeiffer BD, Rubin GM, Truman JW
    eLife. 2015 Jul 20;4:. doi: 10.7554/eLife.04493

    Drosophila central neurons arise from neuroblasts that generate neurons in a pair-wise fashion, with the two daughters providing the basis for distinct A and B hemilineage groups. Thirty three postembryonically-born hemilineages contribute over 90% of the neurons in each thoracic hemisegment. We devised genetic approaches to define the anatomy of most of these hemilineages and to assessed their functional roles using the heat-sensitive channel dTRPA1. The simplest hemilineages contained local interneurons and their activation caused tonic or phasic leg movements lacking interlimb coordination. The next level was hemilineages of similar projection cells that drove intersegmentally coordinated behaviors such as walking. The highest level involved hemilineages whose activation elicited complex behaviors such as takeoff. These activation phenotypes indicate that the hemilineages vary in their behavioral roles with some contributing to local networks for sensorimotor processing and others having higher order functions of coordinating these local networks into complex behavior.

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