Search results for "Coherence"

Non-Parametric Rank Statistics for Spectral Power and Coherence

2019

AbstractDespite advances in multivariate spectral analysis of neural signals, the statistical inference of measures such as spectral power and coherence in practical and real-life scenarios remains a challenge. The non-normal distribution of the neural signals and presence of artefactual components make it difficult to use the parametric methods for robust estimation of measures or to infer the presence of specific spectral components above the chance level. Furthermore, the bias of the coherence measures and their complex statistical distributions are impediments in robust statistical comparisons between 2 different levels of coherence. Non-parametric methods based on the median of auto-/c…

Pre- and post-ictal brain activity characterization using combined source decomposition and connectivity estimation in epileptic children

2019

In this research, the study of functional connectivity between sources of electroencephalogram (EEG) activity assessed for different classes (well before seizure, preictal and post-ictal) was performed. EEG recordings were acquired from 12 subjects with focal epilepsy. Then, ten common spatial patterns (CSP) were obtained for EEG segments describing 95% of Riemannian distance between pairs of classes, followed by estimation of multivariate autoregressive (MVAR) models’ coefficients. The MVAR models were further used to extract coherence as a functional connectivity measures. Our results show that the coherence between CSP sources differs between baseline and pre-ictal segments: it has the l…

Flat-top ultra-wideband photonic filters based on mutual coherence function synthesis

2008

A novel all-incoherent optical circuit that allows for band-pass microwave-photonic filter design is presented and verified through numerical simulation. In contrast to conventional spectrum-sliced optical architectures that operate on the basis of a finite number of discrete taps, our proposal is based on arbitrary shaping of the spectrum of the broadband optical source in a conventional frequency encoder. This fact dramatically increases the free spectral range of the filter with respect to the conventional discrete-time optical processing. The filter transfer function is given by the mutual coherence function of the filtered source which allows, through an inverse problem, sculpting the …

Surrogate Data Analysis for Assessing the Significance of the Coherence Function

2004

In cardiovascular variability analysis, the significance of the coupling between two time series is commonly assessed by setting a threshold level in the coherence function. While traditionally used statistical tests consider only the parameters of the adopted estimator, the required zero-coherence level may be affected by some features of the observed series. In this study, three procedures, based on the generation of surrogate series sharing given properties with the original but being structurally uncoupled, were considered: independent identically distributed (IID), Fourier transform (FT), and autoregressive (AR). IID surrogates maintained the distribution of the original series, while …

High myopic patients with and without foveoschisis: morphological and functional characteristics.

2020

Purpose: Myopic foveoschisis (MF) is characterized by the splitting of the retinal layers in the fovea of patients with high myopia (HM). MF may progress into foveal detachment or macular hole formation with consequent loss of central vision. The aim of this study is to investigate morphological and functional changes of the macular region in myopic subjects with and without foveoschisis. Design: Observational, cross-sectional, comparative study. Methods: Forty-eight patients with HM and 24 healthy controls were evaluated by spectral domain-optical coherence tomography (SD-OCT), multifocal electroretinography (mfERG) and microperimetry (MP-1) tests to assess macular thickness, functionality…

2020

We sought to determine the effects of the use of a Bioengineered Combo Dual-Therapy CD34 Antibody-Covered Sirolimus-Eluting Coronary Stent (Combo® DTS) in patients with chronic total occlusion (CTO) by evaluating clinical outcomes and by performing an optical coherence tomography (OCT) analysis. We retrospectively analyzed data from 39 patients who had successfully undergone OCT-guided revascularization of a CTO being treated with a Combo® DTS. Clinical assessment, angiography (with quantitative coronary angiography analysis) and OCT examination were performed at baseline and at follow-up. The median follow-up period was 189 days, ranging from 157 to 615 days. At follow-up, revascularizatio…

Genetic relationship between five psychiatric disorders estimated from genome-wide SNPs

2013

AM Vicente - Cross-Disorder Group of the Psychiatric Genomics Consortium Most psychiatric disorders are moderately to highly heritable. The degree to which genetic variation is unique to individual disorders or shared across disorders is unclear. To examine shared genetic etiology, we use genome-wide genotype data from the Psychiatric Genomics Consortium (PGC) for cases and controls in schizophrenia, bipolar disorder, major depressive disorder, autism spectrum disorders (ASD) and attention-deficit/hyperactivity disorder (ADHD). We apply univariate and bivariate methods for the estimation of genetic variation within and covariation between disorders. SNPs explained 17-29% of the variance in …

Work satisfaction, psychological resiliency and sense of coherence as correlates of work engagement

2018

The objective of the article is to describe the links between work engagement—the response variable, work satisfaction—the explanatory variable, and sense of coherence, along with resiliency as resources—moderating variables. The theoretical foundations for our hypotheses are Hackman and Oldham’s Job Charcteristics Model, Block and Kremen’s conception of resiliency, Antonovsky’s salutogenesis, the JD-R of relation between work demands and resources and also the model of work engagement in the research of Schaufeli, Salanova, González-romá, and Bakker. Methods: 94 independent workers of Polish branches of international corporations were studied. Work satisfaction was measured using the SSP s…

Supercontinuum optimization for dual-soliton based light sources using genetic algorithms in a grid platform

2014

We present a numerical strategy to design fiber based dual pulse light sources exhibiting two predefined spectral peaks in the anomalous group velocity dispersion regime. The frequency conversion is based on the soliton fission and soliton self-frequency shift occurring during super- continuum generation. The optimization process is carried out by a genetic algorithm that provides the optimum input pulse parameters: wavelength, temporal width and peak power. This algorithm is implemented in a Grid platform in order to take advantage of distributed computing. These results are useful for optical coherence tomography applications where bell-shaped pulses located in the second near-infrared wi…

Geodynamic inversion to constrain the non-linear rheology of the lithosphere

2015

A common method to determine the strength of the lithosphere is through estimating its effective elastic thickness from the coherence between gravity and topography. This method assumes a priori that the lithosphere is a thin elastic plate floating on a viscous mantle. Whereas this seems to work well with oceanic plates, it has given controversial results in continental collision zones. Usually, continental collisions zones are well-studied areas for which additional geophysical datasets such as receiver functions and seismic tomography exist that constrain the geometry of the lithosphere and often show that it is rather complex. Yet, lithospheric geometry by itself is insufficient to under…