Manling Ge

Image reconstruction of EIT using differential evolution algorithm

Differential evolution (DE) algorithm is used in this paper to solve the inverse problem of EIT, where the cost function is determined by solving the forward problem using finite element method (FEM). This method is applied to the 2D impedance reconstruction of brain section based on real head model. Our simulations demonstrate that DE algorithm is robust in obtaining high quality reconstruction for EIT problems studied in this paper.

The comparison between FVM and FEM for EIT forward problem

In this paper, the finite volume method (FVM) is introduced in detail for solving the electrical impedance tomography (EIT) forward problem. A new idea for constructing the primary and secondary elements in FVM is presented. Detailed comparisons between FVM and the finite element method (FEM), including the characteristic of the coefficient matrix and the precision of the results, are carried out under the same mesh system. It is shown that accurate estimates of the potential distribution can be obtained with an FVM solution.

Single trial EEG classification during finger movement task by using hidden Markov models

A new algorithm based on hidden Markov models (HMM) to discriminate single trial electroencephalogram (EEG) between two conditions of finger movement task is proposed. Firstly, multi-channel EEG signals of single trial are filtered in both frequency and spatial domains. The pass bands of the two filters in frequency domain are 0~3 Hz and 8~30 Hz respectively, and the spatial filters are designed by the methods of common spatial subspace decomposition (CSSD). Secondly, two independent features are extracted based on HMM. Finally, the movement tasks are classified into two groups by a perceptron with the extracted features as inputs. With a leave-one out training and testing procedure, an average classification accuracy rate of 93.2% is obtained based on the data from five subjects. The proposed method can be used as an EEG-based brain computer interface (BCI) due to its high recognition rate and insensitivity to noise. In addition, it is suitable for either offline or online EEG analysis

Application of the Directed Transfer Function Method to the Study of the Propagation of Epilepsy Neural Information

A study of the propagation of electroencephalogram (EEG) activity before seizure by means of the Directed Transfer Function (DTF) is presented. The DTF method is a multi-channel parametric method of analysis based on an autoregressive model, and is capable of supplying such information as the direction, spectra and dynamics of the propagation of EEG signals. This method is typically utilized to determine patterns of neural information flow. In this paper, the DTF method is applied to detect the propagation of EEG signals, and the work is focused on aiding the clinical diagnose for the foci and the propagation pathway of the epilepsy neural information. The work has been efficiently utilized to diagnose complex partial seizures originating from temporal and frontal lobe structures in 10 patients, based on the intracranial recordings. It is concluded that the source of the seizure onset, as well as the neural circuitry, can be found so that the propagation of the epileptic information from the foci to the entire brain can be determined. It is tested that the DTF method may be effective and practical in the clinical diagnose.

Study of the effects of 50 Hz homogeneous magnetic field on apoptosis and proliferation of SNU cells in vitro

The biological effects of magnetic field on SNU (human low differentiated gastric adenocarcinoma cell line) cells are studied in this paper. SNU cells were randomly divided into control groups and four treatment groups, the treatment groups were respectively irradiated by 50 Hz ferromagnetic field (0.097 T) 5 min., 30 min., 60 min., and 120 min. We observed the effects on proliferation and apoptosis of SNU cells after the treatment of magnetic field by flow cytometric (FCM) DNA analysis and electron microscope observation. The apoptosis rate in treatment groups are 4.75% /spl plusmn/ 1.24%, 6.50% /spl plusmn/ 0.61%, 9.20% /spl plusmn/ 1.76% and 6.26% /spl plusmn/ 2.95% respectively and significantly higher than that in control group. In the irradiation time range from 5 min to 60 min, there is a significant time-depended response correlation of apoptosis rate( r = 0.97, P < 0.01), but FCM results showed that the effects of 50 Hz homogeneous ferromagnetic field on the proliferation and distribution of cell cycle of SNU cells is not significant. We concluded that irradiation of 50 Hz homogeneous ferromagnetic field could promote apoptosis of SNU cells.

A theoretical computation of abnormal oscillation propagation in a 2-D excitable neuronal network coupled via gap junction

The propagation of abnormal oscillations in actual neural tissue is often irregular and highly complex. The experiments and theoretical work on it are both very difficult; however, it can be helpful to understand some disorder in the neural system. With the help of microelectrode recording techniques and microdialysis, some experimental results from human beings and animal models have demonstrated that epileptic seizures can occur when either the external cellular environment of neurons is changed drastically from physiological conditions or when the synapses of neurons are extensively induced to release neurotransmitter or other neural signals. Here, we present a theoretical framework to investigate the gap junctions (electrical synapse) effect on the propagation of abnormal oscillations. Although such theoretical work is still very limited in explaining all the mechanistic problems related to the disorder situation, e.g., epilepsy, it is, nevertheless, helpful to our understanding of synaptic effects on the abnormal activity propagation. Now, from ionic channels to neural networks, a two-dimensional (2-D) spatial-temporal partial differential equation (PDE) is built. The implicit scheme of the finite-differential method in the time domain and a multistep algorithm are utilized to solve the PDE and the nonlinear ordinary differential equations, respectively, while the successive overrelaxation method is utilized to compute the large-scale sparse equations. Lyapunov exponent and approximate entropy are further applied, respectively, to the analysis of chaos and complexity in the propagation. Numerical results show that abnormal oscillations can propagate when the coupling strength of the gap junctions is sufficiently large, leading to turbulence in the excitable network, and that the larger the coupling strength is, the greater the nonlinear and the complexity of the propagation are. It is also concluded that the chaos and the complexity of the activity at the periphery point are larger than that at the central point when the abnormal oscillations propagate from the central to the periphery. This theoretical work is helpful to understand the gap junctions effects on the abnormal oscillation propagation in a 2-D excitable neural tissue.

An Understanding for the Abnormal Spikes of the EEG Simulation in a 2-D Neural Network

The work here presents an abnormal EEG simulation and an analysis for the abnormal spikes in the simulation by using the wavelet method. The simulation is derived from the electrophysiological model of an excitable neuron being in a disorder process. The spike wave and the multi-spike wave of the EEG morphology are reconstructed by step changes in the concentration of the intracellular calcium ions ([Ca]i). In the further work, when the concentration of [Ca] i is sufficiently large, the multi-spike wave can also be reconstructed and the spikes of the potentials are analyzed by the multi-layer wavelet method. The work will be helpful to understand how the EEG morphology is formed from the microcosmic viewpoint

An Abnormal EEG Simulation Based on The Chay Model of An Excitable Neuron

The work here presents an abnormal EEC simulation by using the electrophysiological model of the neuron. The spike wave and the multi-spike wave of the EEG morphology are reconstructed. The simulation model is derived from the Chay model, which describes the abnormal process in an excitable neuron via bifurcation. The abnormal process, that spiking can be transformed into bursting rapidly, can be observed in some disorder of the nerve system, such as epileptic seizure. The spike wave is simulated by step changes in the bifurcation parameter, which is proportion to the concentration of the intracellular calcium ions (|Ca|1 ). And, when the concentration of (|Ca|1 is sufficiently large, the multi-spike wave can also be reconstructed. The simulation work will be helpful to understand how the EEG morphology is formed from the microcosmic viewpoint

Numeral research of synchronous oscillation on two Chay neurons and 2-D network by gap junction

The relationships of epileptiform waves caused by abnormal neurons are studied and it is an important basis work to investigate the properties of neural disease such as epilepsy. In our work, two Chay neurons and 2-D network models and their chaotic characters are computed in order to study the effect of gap junction on the dynamics of neuron population. The numerical results of nonlinear oscillation are analyzed when neurons are coupled in different states. These states are: repetitive spike neuron and bursting chaotic neuron; bursting chaotic neuron and single bursting neuron; abnormal neuron and resting neuron; neurons randomly distributed in 2-D network. The phase diagram and the dynamic feature of Ca/sup 2+/ concentration are also used to learn the synchronous activities. Our work is helpful to our further research for the mechanism of epileptic waves propagation and the effect of gap junction on 3-D network.

Effects of 50 Hz ferromagnetic field exposure on apoptosis and proliferation of murine liver cell in vivo

The biological effects of irradiation by magnetic field on the proliferation and apoptosis of the liver cells in mice are studied. BALB/C mice were irradiated by 50 Hz homogeneous ferromagnetic field(0.097 T) and divided into four irradiation groups: 5 min., 30 min., 60 min., and 120 min.. Proliferation and apoptosis of the liver cells were analyzed with the flow cytometry (FCM) and DNA agarose gel electrophoresis. The FCM test results showed that different irradiation time of magnetic field could induce apoptosis of murine liver cells. The percentage of apoptosis in irradiation groups are 9.55%/spl plusmn/0.82%, 12.07%/spl plusmn/2.96%, 13.66%/spl plusmn/1.90% and 16.22%/spl plusmn/2.64% respectively and significantly higher than that in control group. In the interval of 5 min-120 min, the percentage of apoptosis of liver cells increased as the irradiation time prolonged (r=0.78, P<0.05), but FCM results showed that 50 Hz homogeneous ferromagnetic field have no effects on proliferation of murine liver cells. We concluded that irradiation of 50 Hz homogeneous ferromagnetic field could induce and promote apoptosis of murine liver cells in time-effects manner.