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A computational model for research on retinal implants is presented. In this model, the electric field produced by a multi-electrode array in a uniform retina is calculated. It is shown how this model can be used to answer questions as to cross talk of activated electrodes, bunching of field lines in monopole and dipole activation, sequential stimulation, multipolar stimulation, etc. The model is...
This paper presents a novel approach to estimate internal variables such as gating variables, potassium, sodium and chloride concentrations from the knowledge of voltage of a neuron. This approach is based on the Hodgkin-Huxley neuron dynamics and basic ideas behind a Luenberger observer, and utilizes the full nonlinear dynamics. Results from numerical simulations are presented.
Early detection of autism spectrum disorder (ASD) in infants is vital in maximizing the impact and potential long-term outcomes of early delivery of rehabilitative therapies. To date no definitive diagnostic test for ASD exists. Electroencephalography is a noninvasive method used to capture underlying electrical changes in brain activity. This proof-of-concept study suggests that recurrence quantification...
Working memory (WM) is necessary for higher cognitive functions. To understand the mechanism of WM from the view of network connectivity becomes a hot topic in the field of neuroscience. The purpose of this work is to develop a sparse causal analysis (SCA) based on non-negative matrix factorization (NMF), and to investigate dynamic connections among the multi-channel spikes during WM. 16-channels...
Neural mass models (NMM) provide insights into the neuromodulatory mechanisms underlying alterations of cortical activity as recorded by electroencephalography (EEG). In the human primary motor cortex (M1), neuromodulation can be induced by non-invasive brain stimulation (NIBS). We aimed to capture the origin of NIBS-induced alterations in the EEG power spectrum using a thalamocortical NMM. We found...
The mechanisms behind memory have been studied mainly in artificial neural networks. Several mechanisms have been proposed, but it remains unclear yet if and how these findings can be translated to biological networks. Here we unravel part of the mechanism by showing that cultured neuronal networks develop an activity connectivity balance. External inputs disturb this balance and induce connectivity...
Neurons are capable, when the summation of excitatory inputs in dendrites is locally non-linear, to perform linearly non-separable classifications. What is the minimum set of vectors which can be linearly non-separable? How well neurons without dendrite approximate these classifications? The present paper tackles these problems which could strengthen or weaken the impact of dendrites on computation...
In this study, we propose unsupervised learning of the lateral inhibition structure through inhibitory spike-timing dependent plasticity (iSTDP) in a computational model for multivariate data processing inspired by the honeybee antennal lobe. After exposing the network to a sufficient number of input samples, the inhibitory connectivity self-organizes to reflect the correlation between input channels...
Several experimental results published in the literature showed that weak pulsed magnetic fields affected the response of the central nervous system. However, the specific biological mechanisms that regulate the observed behaviors are still unclear and further scientific investigation is required. In this work we performed simulations on neuronal models exposed to a specific pulsed magnetic field...
A modeling framework for the neuromuscular system unifying five components is presented. The components are: (1) a biophysical model of the motoneuron pool predicting motor unit recruitment and motor unit firing times; (2) a biophysically based description of the excitation-contraction coupling in the sarcomeres, which determines the cross-bridge-cycling induced stress of a sarcomere; (3) action potential...
Human walking involves considerable cortical control, but brain imaging technology has not previously enabled investigation of brain networks during locomotion. We combined experimental electroencephalography (EEG) analysis of 18 subjects and neural mass modeling approaches to investigate functional neural connectivity during walking on uneven terrain. Both approaches revealed a pattern of connectivity...
Extracellular action potentials (EAPs) must be classified before they can yield any useful information on neuronal function and organization. Neuronal source classification therefore represents a critical step in the analysis of electrophysiological data. This study demonstrates the efficacy of a multi-sensor EAP classification scheme using source location as a classification feature. Localization...
Transcranial magnetic stimulation (TMS) has been used to study brain function and is being investigated as a possible treatment for a variety of neurological disorders and neuropsychiatric diseases. Most studies implementing TMS utilize adult subjects but the method may also be a beneficial tool in the treatment of pediatric patients. It is known that the structure of pediatric brains differ to those...
Transcranial Magnetic Stimulation (TMS), transcranial Direct Current Stimulation (tDCS), and other electromagnetic stimulation modalities have been used to apply neuromodulation but their working mechanism remains largely unknown. This study aims to introduce a computer model for membrane potential dynamics induced by electromagnetic stimulation. In the simulation, realistic neuron morphologies are...
In order to judiciously compare neural responses between repeated trials or stimuli, a well-suited distance metric is necessary. With multi-electrode recordings, a neural response is a spatiotemporal pattern, but not all of the dimensions of space and time should be treated equally. In order to understand which dimensions of the input are more discriminative and to improve the classification performance,...
The objective of the study was to investigate the electrochemical properties of porous titanium nitride electrodes in vivo and in vitro for a period of 53 days. Four electrodes were implanted in two pigs and four electrodes were kept in phosphate buffered saline at 37.5 °C. Electrochemical impedance spectroscopy, voltage transient measurements, cyclic voltammetry and electrical stimulation were applied...
Regenerative peripheral nerve interfaces (RPNIs) transfer motor and sensory signals between amputee and prosthesis. Von Frey (VF) monofilaments are used clinically to evaluate sensory feedback but have not been validated at locations used in our rodent studies. Our purposes were to determine VF sensory test reliability at the ankle and thigh, and to evaluate sensory function of Mixed Nerve (MN) and...
Myoelectric pattern recognition (PR) can provide a more intuitive control for upper limb amputees in using multifunction prosthesis than direct control. Accuracy of a pattern recognition system has been shown to improve with increasing number of EMG channels. However, increasing the number of channels comes with a drawback of increased weight, cost and complexity of the prosthesis. This paper presents...
Electrical stimulation of the cervical vagus nerve is an established treatment for therapy refractory epilepsy and, more recently, for depression and congestive heart failure. To overcome risks in implantation of neurostimulation devices as well as to extend application areas, less invasive techniques have been developed affecting the auricular branch of the vagus nerve (ABVN). This includes transcutaneous...
Loss of somatosensory function is detrimental to quality of life and is related to the loss of functional ability. Restoring sensitivity would have great potential in medicine. Previous work has demonstrated that the application of subsensory electrical noise can enhance sensitivity to a distal mechanical stimulus. In this paper we aimed to uncover the mechanism behind this enhancement. Two studies...
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