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A significant contributor to artefact generation in surface electromyography (sEMG) and, functional electrical stimulation (FES) intensity is the skin-to-electrode impedance (ZSE/). While using electrolytic gels may initially lower ZSE/, the impedance may not remain stable. It can vary over time due to changes in underlying structures such as sweat glands and physical deformations due to movements...
Laplacian Electrocardiogram (LECG) is a non-invasive approach providing high spatiotemporal distributed information of cardiac electrical activity. Recently researchers have recorded surface potentials from monopolar disc electrodes to estimate the Laplacian using finite difference algorithms or spline surface Laplacian estimators. Bipolar and quasi-bipolar electrodes have also been used to record...
Ventricular fibrillation (VF) can be synchronized with a novel synchronized pacing technique (SyncP) using low-energy pacing pulses, which causes pace termination of VF. Synchronized pacing (SyncP) is defined as optical recording guided real-time detection and stimulation of spatiotemporal excitable gaps. In this paper, we investigate the effect of post-shock SyncP strategy on improvement of defibrillation...
Studies have investigated the effect of defibrillator paddle position on the efficacy of external electrocardioversion of atrial fibrillation, without agreeing upon an optimal placement. We wish to investigate using esophageal electric fields (EEFs) to predict atrial defibrillation thresholds (ADFTs) on a patient-specific basis. We propose to (1) investigate the relationship between EEFs and ADFTs...
Previous studies have shown that successful defibrillation depends on the uniformity of current density in the heart and the percentage of total current reaching the heart. This study uses an anatomically-realistic finite element computer model of the human torso for external atrial defibrillation to (1) examine the defibrillation energy thresholds and current density distributions for common clinical...
A multi-input modeling approach is introduced to quantify hippocampal neural dynamics. It is based on the Volterra modeling approach extended to multiple inputs. The computed Volterra kernels allow quantitative description of hippocampal transformations and define a predictive model that can produce responses to arbitrary input patterns. Electrophysiological data from several CA3 and CA1 cells in...
In the framework of cardiac pacing, measured chronaxies are different for current and for voltage pulses. They increase with the distance between the pacing cathode and the myocardium, and with the size of the electrode. Mathematical formulae that relate the time constants (and the chronaxies) of the strength duration curves with the parameters of the system composed by the electrode, the volume conductor...
The water content of stratum corneum (SC) has been reported to vary depending on the anatomical sites. Each anatomical site respectively have their own proper water content of SC which reflects the status of skin health. Also, this anatomical region can be divided into relatively wet and dry area according to the degree of the water content of SC. In this study, we tried to investigate time series...
We describe the development and first tests of ENOBIO, a dry electrode sensor concept for biopotential applications. In the proposed electrodes the tip of the electrode is covered with a forest of multi-walled carbon nanotubes (CNTs) that can be coated with Ag/AgCl to provide ionic-electronic transduction. The CNT brush-like structure is to penetrate the outer layers of the skin improving electrical...
Future cochlear implants demand a higher density of stimulation sites (electrodes) and enhanced functionality (e.g. feedback information). The current generation of implanted cochlear prostheses is making use of a completely "passive scheme" and cannot meet these requirements. An "all-silicon" concept integrating active components with passive electrodes in silicon has been proposed...
Volume imaging, defibrillation electrode models, and finite element modeling are employed in patient-specific procedural modeling in pediatric patients with cardiac arrhythmias. Due to variable size and anatomy, these patients may not be well-served by devices designed for adult defibrillation. A pipeline for rapid creation of image based models that can be interactively interrogated to determine...
A communication support interface controlled by eye movements and voluntary eye blink has been developed for disabled individuals with motor paralysis who cannot speak. Horizontal and vertical electro-oculograms were measured using two electrodes attached above and beside the dominant eye and referring to an earlobe electrode and amplified with AC-coupling in order to reduce the unnecessary drift...
Catheter-based epicardial mapping is possible with two access methods: transthoracic access and transvenous access. Transthoracic access requires lengthy sequential mapping procedures and stable arrhythmias. Transvenous access uses the multielectrode (4-to-20 electrodes) catheters placed in the coronary veins, however, leaves most of the epicardium inaccessible to direct measurement. The aim of this...
On theoretical grounds, interstitial current injected and removed using electrodes in close proximity does not cross the membrane, while equilibration of intracellular and interstitial potentials occurs distant from electrodes widely separated. Multisite interstitial stimulation should therefore give rise to interstitial potential differences recorded centrally that depend on intracellular and interstitial...
We present a forward problem formulation for computing biopotentials measured with dry or capacitive electrodes. This formulation is not quasistatic and has mixed boundary conditions. Our results show that simple approximations to the measurements based on capacitive coupling are adequate in most situations. We study the range of validity and errors committed in the EEG forward and inverse problems...
Artifact removal is an essential part in electroencephalogram (EEG) recording and the raw EEG signals require preprocessing before feature extraction. In this work, we implemented three filtering methods and demonstrated their effects on the performance of different classifiers. Bandpass digital filtering, median filtering and facet method are three preprocessing approaches investigated in this paper...
This paper presents a real-time electro-encephalogram (EEG) identification system with the goal of achieving hands free control. With two EEG electrodes placed on the scalp of the user, EEG signals are amplified and digitised directly using a ProComp+ encoder and transferred to the host computer through the RS232 interface. Using a real-time multilayer neural network, the actual classification for...
Brain-machine interfaces (BMIs) have shown promise in augmenting people's control of their surroundings, especially for those suffering from paralysis due to neurological disorders. This paper describes an experiment using the rodent model to explore information available in neural signals recorded from chronically implanted intracortical microelectrode arrays. In offline experiments, a number of...
Prolonged electrical stimulation can lead to temporary or permanent changes in neural response. Stimulation of neurons at levels sufficient to cause overlapping zones of excitation can induce multiple effects, leading to permanent damage to neurons or temporary depression not detectable through histopathological analysis. The present study focuses on determining the effects of prolonged, continuous...
Rheoencephalography (REG) is impedance plethysmography applied to the head, and provides an indirect measurement of the pulsatility of the cerebral blood volume. To extend REG as a clinical and research tool, it is necessary to evaluate the sensitivity of REG measurement to local brain conductivity changes. By means of the analytical solution of a four-sphere geometrical model of the head, maps of...
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