scholarly journals Ghost interactions in MEG/EEG source space: A note of caution on inter-areal coupling measures

2017 ◽  
Author(s):  
J. Matias Palva ◽  
Sheng H. Wang ◽  
Satu Palva ◽  
Alexander Zhigalov ◽  
Simo Monto ◽  
...  
Keyword(s):  
Fundamental Problem ◽  
Region Of Interest ◽  
List Type ◽  
Volume Conduction ◽  
Source Modeling ◽  
Large Numbers ◽  
Long Range Interactions ◽  
Coupling Techniques ◽  
Amplitude Correlation ◽  
Linear Correlations

AbstractWhen combined with source modeling, magneto‐ (MEG) and electroencephalography (EEG) can be used to study long-range interactions among cortical processes non-invasively. Estimation of such inter-areal connectivity is nevertheless hindered by instantaneous field spread and volume conduction, which artificially introduce linear correlations and impair source separability in cortical current estimates. To overcome the inflating effects of linear source mixing inherent to standard interaction measures, alternative phase‐ and amplitude-correlation based connectivity measures, such as imaginary coherence and orthogonalized amplitude correlation have been proposed. Being by definition insensitive to zero-lag correlations, these techniques have become increasingly popular in the identification of correlations that cannot be attributed to field spread or volume conduction. We show here, however, that while these measures are immune to the direct effects of linear mixing, they may still reveal large numbers of spurious false positive connections through field spread in the vicinity of true interactions. This fundamental problem affects both region-of-interest-based analyses and all-to-all connectome mappings. Most importantly, beyond defining and illustrating the problem of spurious, or “ghost” interactions, we provide a rigorous quantification of this effect through extensive simulations. Additionally, we further show that signal mixing also significantly limits the separability of neuronal phase and amplitude correlations. We conclude that spurious correlations must be carefully considered in connectivity analyses in MEG/EEG source space even when using measures that are immune to zero-lag correlations.Highlights✓Reliable estimation of neuronal coupling with MEG and EEG is challenged by signal mixing✓A number of coupling techniques attempt to overcome this limitation by excluding zero-lag interactions✓Contrary to what is commonly admitted, our simulations illustrate that such interaction metrics will still yield false positives✓Spurious, or “ghost”, interactions are generally detected between sources in the vicinity of true phase-lagged interacting sources✓Signal mixing also severely affects the mutual separability of phase and amplitude correlations

scholarly journals Cross-reactive, natural IgG recognizing L. major promote parasite internalization by dendritic cells and promote protective immunity

2021 ◽  
Author(s):  
Filiz Dermicik ◽  
Susanna Lopez Kostka ◽  
Stefan Tenzer ◽  
Ari Waisman ◽  
Esther Von Stebut
Keyword(s):  
Dendritic Cells ◽  
B Cell ◽  
Protective Immunity ◽  
Normal Mouse ◽  
Leishmania Major ◽  
Mouse Serum ◽  
List Type ◽  
Susceptibility To Infection ◽  
Large Numbers

Abstract In cutaneous leishmaniasis, infection of dendritic cells (DC) is essential for generation of T cell-dependent protective immunity. DC acquires Leishmania major through Fc receptor (FcR)-mediated uptake of complexes comprising antibodies bound to parasites. We now assessed the development of the initial B cell and DC response to the parasite itself and if natural IgG play a role. L. major parasites display large numbers of phospholipids on their surface. Parasites were opsonized with normal mouse serum (NMS), or serum containing anti-phospholipid IgG (PL). We found that L. major bound to PL which significantly enhanced parasite phagocytosis by DC as compared to NMS. Similar results were obtained with cross-reactive human PL antibodies using myeloid primary human DC. In addition, mice infected with PL-opsonized parasites showed significantly improved disease outcome compared to mice infected with NMS-opsonized parasites. Finally, IgMi mice, which produce membrane-bound IgM only and no secreted antibodies, displayed increased susceptibility to infection as compared to wild types. Interestingly, once NMS was administered to IgMi mice, their phenotype was normalized to that of wild types. Upon incubation with IgG-opsonized parasite (IgG derived from infected mice or using PL antibodies), also the IgMi mice were able to show superior immunity. Our findings suggest that “natural” cross-reactive antibodies (e.g., anti-PL Ab) in NMS bind to pathogens to facilitate phagocytosis, which leads to induction of protective immunity via preferential DC infection. Prior L. major-specific B cell-priming does not seem to be absolutely required to facilitate clearance of this important human pathogen in vivo. Key messages We found that anti-phospholipid (anti-PL) antibodies enhance phagocytosis of L. major by DCs. We also found that normal mouse sera have natural antibodies that can imitate PL specific antibodies. Using different genetically modified mice, we found that these antibodies can be IgG, not only IgM.

scholarly journals Strong Law of Large Numbers for a Function of the Local Times of a Transient Random Walk in $${\mathbb {Z}}^d$$

2019 ◽  
Vol 33 (4) ◽  
pp. 2315-2336
Author(s):  
Inna M. Asymont ◽  
Dmitry Korshunov
Keyword(s):  
Random Walk ◽  
Law Of Large Numbers ◽  
Acta Math ◽  
Local Times ◽  
List Type ◽  
Strong Law ◽  
Statistics And Probability ◽  
Large Numbers ◽  
Berkeley Symposium ◽  
Transient Random Walk

Abstract For an arbitrary transient random walk $$(S_n)_{n\ge 0}$$ ( S n ) n ≥ 0 in $${\mathbb {Z}}^d$$ Z d , $$d\ge 1$$ d ≥ 1 , we prove a strong law of large numbers for the spatial sum $$\sum _{x\in {\mathbb {Z}}^d}f(l(n,x))$$ ∑ x ∈ Z d f ( l ( n , x ) ) of a function f of the local times $$l(n,x)=\sum _{i=0}^n{\mathbb {I}}\{S_i=x\}$$ l ( n , x ) = ∑ i = 0 n I { S i = x } . Particular cases are the number of visited sites [first considered by Dvoretzky and Erdős (Proceedings of the Second Berkeley Symposium on Mathematical Statistics and Probability, pp 353–367, 1951)], which corresponds to the function $$f(i)={\mathbb {I}}\{i\ge 1\}$$ f ( i ) = I { i ≥ 1 } ; $$\alpha $$ α -fold self-intersections of the random walk [studied by Becker and König (J Theor Probab 22:365–374, 2009)], which corresponds to $$f(i)=i^\alpha $$ f ( i ) = i α ; sites visited by the random walk exactly j times [considered by Erdős and Taylor (Acta Math Acad Sci Hung 11:137–162, 1960) and Pitt (Proc Am Math Soc 43:195–199, 1974)], where $$f(i)={\mathbb {I}}\{i=j\}$$ f ( i ) = I { i = j } .

scholarly journals Fast Pedestrian Recognition Based on Multisensor Fusion

2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
Hongyu Hu ◽  
Zhaowei Qu ◽  
Zhihui Li ◽  
Jinhui Hu ◽  
Fulu Wei
Keyword(s):  
Region Of Interest ◽  
Recognition Algorithm ◽  
Support Vector ◽  
Svm Classifier ◽  
Multisensor Fusion ◽  
Feature Extraction Method ◽  
Urban Road ◽  
Histograms Of Oriented Gradients ◽  
Large Numbers ◽  
Candidate Regions

A fast pedestrian recognition algorithm based on multisensor fusion is presented in this paper. Firstly, potential pedestrian locations are estimated by laser radar scanning in the world coordinates, and then their corresponding candidate regions in the image are located by camera calibration and the perspective mapping model. For avoiding time consuming in the training and recognition process caused by large numbers of feature vector dimensions, region of interest-based integral histograms of oriented gradients (ROI-IHOG) feature extraction method is proposed later. A support vector machine (SVM) classifier is trained by a novel pedestrian sample dataset which adapt to the urban road environment for online recognition. Finally, we test the validity of the proposed approach with several video sequences from realistic urban road scenarios. Reliable and timewise performances are shown based on our multisensor fusing method.

scholarly journals Correctness of Sequential Monte Carlo Inference for Probabilistic Programming Languages

2021 ◽  
pp. 404-431
Author(s):  
Daniel Lundén ◽  
Johannes Borgström ◽  
David Broman
Keyword(s):  
Monte Carlo ◽  
Programming Languages ◽  
Sequential Monte Carlo ◽  
Fundamental Problem ◽  
Operational Semantics ◽  
Correctness Proof ◽  
Probabilistic Programming ◽  
Inference Problems ◽  
Large Numbers ◽  
Open Question

AbstractProbabilistic programming is an approach to reasoning under uncertainty by encoding inference problems as programs. In order to solve these inference problems, probabilistic programming languages (PPLs) employ different inference algorithms, such as sequential Monte Carlo (SMC), Markov chain Monte Carlo (MCMC), or variational methods. Existing research on such algorithms mainly concerns their implementation and efficiency, rather than the correctness of the algorithms themselves when applied in the context of expressive PPLs. To remedy this, we give a correctness proof for SMC methods in the context of an expressive PPL calculus, representative of popular PPLs such as WebPPL, Anglican, and Birch. Previous work have studied correctness of MCMC using an operational semantics, and correctness of SMC and MCMC in a denotational setting without term recursion. However, for SMC inference—one of the most commonly used algorithms in PPLs as of today—no formal correctness proof exists in an operational setting. In particular, an open question is if the resample locations in a probabilistic program affects the correctness of SMC. We solve this fundamental problem, and make four novel contributions: (i) we extend an untyped PPL lambda calculus and operational semantics to include explicit resample terms, expressing synchronization points in SMC inference; (ii) we prove, for the first time, that subject to mild restrictions, any placement of the explicit resample terms is valid for a generic form of SMC inference; (iii) as a result of (ii), our calculus benefits from classic results from the SMC literature: a law of large numbers and an unbiased estimate of the model evidence; and (iv) we formalize the bootstrap particle filter for the calculus and discuss how our results can be further extended to other SMC algorithms.

scholarly journals Integrating Plant Trials into Teaching and Student Research Programs

2001 ◽  
Vol 11 (3) ◽  
pp. 385-388
Author(s):  
Michael A. Arnold ◽  
R. Daniel Lineberger ◽  
Tim D. Davis ◽  
Steven W. George ◽  
Wayne A. Mackay ◽  
...  
Keyword(s):  
Statistical Design ◽  
Region Of Interest ◽  
Early Years ◽  
Professional Communication ◽  
Successful Implementation ◽  
Student Research ◽  
Assistance Programs ◽  
Large Numbers ◽  
Data Collection And Analysis ◽  
Plant Trials

Plant trialing and marketing assistance programs have become popular in recent years with several state and some regional programs emerging. Successful implementation requires considerable labor, facilities, and monetary resources for evaluation of large numbers of taxa over several years to ensure that plants are well adapted to the region of interest. Research and development funds, dedicated facilities, and cooperator commitment to trialing programs can be limiting during the early years of the programs. Involvement in plant trialing programs allows students to be exposed to plot layout planning, statistical design, plant maintenance, data collection and analysis, and professional communication of trial results. Construction of facilities for conducting plant trials, growing plants for use in trials, trial installation, and maintenance of plants all provide practical hands-on horticultural training. Replicated plant trials provide the latest information on regionally adapted taxa for inclusion in classroom instruction and publications. Plant trialing programs benefit from labor assistance, development of dedicated facilities, and the opportunity to share equipment and supplies among teaching, trialing, and student research projects.

Collective behaviour

2021 ◽  
pp. 94-101
Author(s):  
Adrian P Sutton
Keyword(s):  
Plastic Deformation ◽  
Ballistic Transport ◽  
Theory Of Elasticity ◽  
Atomic Scale ◽  
Length Scales ◽  
New Science ◽  
Large Numbers ◽  
Deformation And Fracture ◽  
Long Range Interactions ◽  
Reductionist Approach

At each change of length-sale in a material new science emerges. The reductionist approach focuses on the atomic and electronic length scales in the belief that a fundamental understanding can be achieved only at this smallest scale. It is blind to the emergence of science no less fundamental at larger length scales resulting from interactions between very large numbers of atoms and defects. While the atomic scale always remains important, a complete understanding of plastic deformation and fracture involves long-range interactions between defects described by the theory of elasticity. Even the mechanism of electronic conduction in a metal changes from ballistic transport at the nanoscale to the diffusive transport of Ohm’s law at the macroscale.

scholarly journals INTRINSIC PHASE-DECOHERENCE OF ELECTRONS BY TWO-LEVEL SYSTEMS

2002 ◽  
Vol 16 (14) ◽  
pp. 511-517 ◽  
Author(s):  
VIPIN SRIVASTAVA ◽  
RAISHMA KRISHNAN
Keyword(s):  
Phase Shift ◽  
Inelastic Scattering ◽  
Low Temperatures ◽  
Fundamental Problem ◽  
Scattering Rate ◽  
Phase Saturation ◽  
Long Range Interactions ◽  
Two Level Systems ◽  
Phase Decoherence ◽  
Dynamic Components

The fundamental problem of the phase saturation of electrons in a disordered mesoscopic system at very low temperatures is addressed. The disorder in the medium has both static and dynamic components, the latter being in the form of two-level systems (TLSs) which become just about the only source of inelastic scattering in the limit T → 0. We propose that besides the inelastic nature of scattering from the TLSs, the phase shift of the electrons is also affected by the nature of tunneling in the TLSs. The tunneling becomes incoherent as T decreases due to increasing long-range interactions among the TLSs which affects the phase coherence of electrons scattering from them. The competition between this effect, which increases as ~ T-1, and that of the scattering rate [Formula: see text] behaving as ~ T apparently govern the phase shift of the electrons.

scholarly journals Topography, Spectral Characteristics, and Extra-to-Intracranial Propagation Pathways of EMG

2019 ◽  
Author(s):  
J. Lahr ◽  
L.D.J. Fiederer ◽  
O. Glanz ◽  
A. Schulze-Bonhage ◽  
T. Ball
Keyword(s):  
Spectral Power ◽  
Brain Activity ◽  
Spectral Characteristics ◽  
Signal Propagation ◽  
Emg Activity ◽  
List Type ◽  
Intracranial Volume ◽  
Volume Conduction ◽  
Temporal Muscle ◽  
The Individual

AbstractObjectiveIntracranial EEG (iEEG) plays an increasingly important role in neuroscientific research and can provide informative control signal for brain-machine interfaces (BMI). While it is clear that electromyographic (EMG) activity of extracranial origin reaches intracranial recordings, the topographic and spectral characteristics of intracranial EMG have been scarcely investigated. It is currently unclear how these characteristics compare to those of physiological brain activity. Little is also known about the exact pathways of extra- to intracranial volume conduction, including the role of craniotomy defects.MethodsIn 5 epilepsy patients under invasive pre-neurosurgical EEG monitoring, we examined chewing-related effects (ChREs) as a source of intracranial EMG activity and compared those effects with physiological brain activity of 9 patients during several behavioural tasks. These included speech production, finger movements, and music perception. Further, we analyzed the association of craniotomy defects (burr-holes and saw-lines) and the intracranial EMG-effects based on the individual post-operative images.ResultsChRE presented with a spatially smooth distribution across almost all intracranial electrodes with the maximum below the temporal muscle. In contrast, the responses of neural origin were spatially more focalized. ChREs were broad-banded and had a higher spectral power and affected higher frequencies than event-related neural activity. ChRE were largely independent of the individual configuration of craniotomy defects. However, we found indications that the silicone sheet, in which electrocorticography (ECoG) electrodes are embedded, attenuates EMG influences, when sufficiently large.ConclusionThe present work is the first comprehensive evaluation of topographic and spectral characteristics of EMG effects in iEEG based on a large sample of subjects. It shows that chewing-related EMG can affect iEEG recordings with higher power than typical physiological brain activity, especially in higher spectral frequencies. As the topographic pattern of ChRE is largely independent of the individual position of craniotomy defects, a direct pathway of volume conduction through the intact skull plays an important role for extra- to-intracranial signal propagation. Intracranial EMG activity related to natural behavior should be accounted for in neuroscientific and BMI applications, especially when based on high-frequency iEEG components. A detailed knowledge of EMG properties may help to design both EMG-reducing algorithms and ECoG grids with a high shielding factor.HighlightsFirst comprehensive description of chewing-related EMG artifacts in iEEG recordingsEMG artifacts and brain activity have distinct topographic and spectral iEEG characteristicsChewing EMG reaches the brain with higher spectral power than task-related brain activityChewing-related EMG artifacts are largely independent of the the position of craniotomy defects

scholarly journals A target enrichment bait set for studying relationships among ostariophysan fishes

2018 ◽  
Author(s):  
Brant C. Faircloth ◽  
Fernando Alda ◽  
Kendra Hoekzema ◽  
Michael D. Burns ◽  
Claudio Oliveira ◽  
...  
Keyword(s):  
Genome Assembly ◽  
Sequence Data ◽  
Evolutionary Relationships ◽  
List Type ◽  
Target Enrichment ◽  
Large Numbers ◽  
Ostariophysan Fishes ◽  
Nuclear Loci ◽  
Enrichment Experiments ◽  
Low Coverage

SummaryTarget enrichment of conserved nuclear loci has helped reconstruct evolutionary relationships among a wide variety of species. While there are preexisting bait sets to enrich a few hundred loci across all fishes or a thousand loci from acanthomorph fishes, no bait set exists to enrich large numbers (>1000 loci) of ultraconserved nuclear loci from ostariophysans, the second largest actinopterygian superorder.In this manuscript, we describe how we designed a bait set to enrich 2,708 ultraconserved nuclear loci from ostariophysan fishes by combining an existing genome assembly with low coverage sequence data collected from two ostariophysan lineages.We perform a series of enrichment experiments using this bait set across the ostariophysan Tree of Life, from the deepest splits among the major groups (>150 MYA) to more recent divergence events that have occured during the last 50 million years.Our results demonstrate that the bait set we designed is useful for addressing phylogenetic questions from the origin of crown ostariophysans to more recent divergence events, and our in silico results suggest that this bait set may be useful for addressing evolutionary questions in closely related groups of fishes, like Clupeiformes.

scholarly journals QuickFigures: A toolkit and ImageJ PlugIn to quickly transform microscope images into scientific figures

PLoS ONE ◽  
2021 ◽  
Vol 16 (11) ◽  
pp. e0240280
Author(s):  
Gregory Mazo
Keyword(s):  
Fluorescent Microscopy ◽  
Region Of Interest ◽  
File Format ◽  
Object Type ◽  
Large Numbers ◽  
Adobe Illustrator ◽  
Time Required ◽  
Free Open Source ◽  
Microscopy Images ◽  
Imagej Plugin

Publications involving fluorescent microscopy images generally contain many panels with split channels, merged images, scale bars and label text. Similar layouts of panels are used when displaying other microscopy images, electron micrographs, photographs, and other images. Assembling and editing these figures with even spacing, consistent font, text position, accurate scale bars, and other features can be tedious and time consuming. In order to save time, I have created a toolset and ImageJ Plugin called QuickFigures. QuickFigures includes many helpful features that streamline the process of creating, aligning, and editing scientific figures. Those features include tools that automatically create split channel figures from a region of interest (“Quick Figure” button and “Inset Tool”), layouts that make it easy to rearrange panels, multiple tools to align objects, and “Figure Format” menu options that help a user ensure that large numbers of figures have consistent appearance. QuickFigures was compared to previous tools by measuring the amount of time needed for a user to create a figure using each software (QuickFigures, OMERO.figure. EZFig, FigureJ and PowerPoint). QuickFigures significantly reduced the amount of time required to create a figure. The toolsets were also compared by checking each software against a list of features. QuickFigures had the most extensive set of features. Therefore, QuickFigures is an advantageous alternative to traditional methods of constructing scientific figures. After a user has saved time by creating their work in QuickFigures, the figures can be exported to a variety of formats including PowerPoint, PDF, SVG, PNG, TIFF and Adobe Illustrator. Export was successfully tested for each file format and object type. Exported objects and text are editable in their target software, making them suitable for sharing with collaborators. The software is free, open source and can be installed easily.

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