Özer, Mahmut

Bildiri | 2003 | Mathematical and Computational Applications8 ( 1-3 ) , pp.71 - 78

In this study, phase-plane analysis is carried out for a simplified model of Purkinje cell dendrite in terms of voltage-gated ionic channels involved. State variables, nullclines and equilibrium points of the model are determined, and effects of ionic channel conductance and injected current on the shape of nullclines and the equilibrium points are investigated. In this study, phase-plane analysis is carried out for a simplified model of Purkinje cell dendrite in terms of voltage-gated ionic channels involved. State variables, nullclines and equilibrium points of the model are determined, and effects of ionic channel conductance and . . . injected current on the shape of nullclines and the equilibrium points are investigated Daha fazlası Daha az

Özer, Mahmut | Erdem, Rıza | Provaznik, Ivo

Makale | 2004 | NeuroReport15 ( 2 ) , pp.335 - 338

Voltage-gated ion channels are of great importance in the generation and propagation of electrical signals in the excitable cell membranes. How these channels respond to changes in the potential across the membrane has been a challenging problem, and different approaches have been proposed to address the mechanism of voltage sensing and gating in these channels. In this study, we attempt a new approach by considering a simple two-state gate system and applying the path probability method to construct a nonequilibrium statistical mechanical model of the system. The model which is based on the principles of statistical physics provide . . .s a firm physical basis for ion channel gating. © 2004 Lippincott Williams & Wilkins Daha fazlası Daha az

Özer, Mahmut

Bildiri | 2004 | GLOBAL ANALYSIS AND APPLIED MATHEMATICS729 , pp.362 - 368

We previously proposed a method for the study of the relaxation phenomena in the activation and inactivation gates of ion channels present in the excitable membranes of neurons. In order to study the relaxation phenomena, the assumption is made that the activation and inactivation gate order parameters can be treated as fluxes and forces. In the present paper, we extend the previous model as including an ensemble of gating particles, and apply it for T-type calcium channel in thalamic relay neurons. It is found that kinetic equations are characterized by two relaxation times. The kinetic coefficients are determined for its empirical . . . model. We also determine the kinetic coefficients of linear and nonlinear thermodynamic models for the same T-type calcium channel, and compare them with the empirical ones Daha fazlası Daha az

Özer, Mahmut | Uzuntarla, Muhammet | Perc, Matjaž | Graham, Lyle J.

Makale | 2009 | Journal of Theoretical Biology261 ( 1 ) , pp.83 - 92

Baysal, Veli | Özer, Mahmut | Yılmaz, Ergin

Bildiri | 2017 | 2017 Medical Technologies National Conference, TIPTEKNO 20172017-January , pp.1 - 4

In this paper, the effects of autapse (a kind of synapse formed between the axon or soma of a neuron and its own dendrites) on the weak signal detection capacity of a Hodgkin-Huxley (H-H) neuron are investigated. In the study, we consider that the H-H neuron has an inhibitory autapse modeled as a chemical synapse. The subthreshold sine wave is injected to the H-H neuron as a weak signal. Obtained results indicate that inhibitory autapse prominently increases the weak signal detection capacity of a H-H neuron when the proper autaptic time delay and autaptic conductance values are choosen. © 2017 IEEE.

Özer, Mahmut | Provaznik, Ivo

Makale | 2005 | JOURNAL OF THEORETICAL BIOLOGY233 ( 2 ) , pp.237 - 243

The precise form of the rate constant functions of ion channels is very crucial for reproducing the electrophysiological behavior. Therefore, how well they account for experimental data plays an important role in the behavior of the model. In this study, we derive kinetic coefficients of activation and inactivation gates in ion channels by Onsager reciprocity theorem for an ensemble of gating particles, and propose that the obtained kinetic coefficients can be used as a comparative tool for the empirical validity of fitted rate constant functions to experimental data. We also illustrate its applicability based on the activation and . . .inactivation kinetics of T-type calcium channel in thalamic relay neurons. We show that the shape of the steady-state curve by itself seems to be a poor indicator of the functional form of the rate functions, but the time constant curves reflect considerable variation depending on the particular form of the rate functions, and that the kinetic coefficients related to the time constants provide a powerful tool to determine the empirical validity of the fitted rate constants. (C) 2004 Elsevier Ltd. All rights reserved Daha fazlası Daha az

Çalım, Ali | Uzuntarla, Muhammet | Özer, Mahmut

Bildiri | 2014 | 2014 22nd Signal Processing and Communications Applications Conference, SIU 2014 - Proceedings , pp.1991 - 1994

In this study, the information coding issue in the nervous system is investigated. By using mathematical equations for modeling the dynamics of the basic units of the system, which are neurons, the information processing performance of the neuron populations is systematically studied. As most of studies in the literature investigate the subject by considering neuron populations as homogenous systems, in this study, the populations are considered as heterogeneous in terms of neuronal excitability. The obtained results demonstrate that considering the heterogeneity of the populations provides significant advantages for the processing . . .of neuronal information. It is shown that the neuron population exhibits maximal performance (resonance) for two different levels of network heterogeneity. Moreover, the influences of other biological parameters, forming the whole system, on this double-resonance phenomenon are investigated. © 2014 IEEE Daha fazlası Daha az

Orhan, Umut | Hekim, Mahmut | Özer, Mahmut

Makale | 2011 | Expert Systems with Applications38 ( 10 ) , pp.13475 - 13481

We introduced a multilayer perceptron neural network (MLPNN) based classification model as a diagnostic decision support mechanism in the epilepsy treatment. EEG signals were decomposed into frequency sub-bands using discrete wavelet transform (DWT). The wavelet coefficients were clustered using the K-means algorithm for each frequency sub-band. The probability distributions were computed according to distribution of wavelet coefficients to the clusters, and then used as inputs to the MLPNN model. We conducted five different experiments to evaluate the performance of the proposed model in the classifications of different mixtures of . . . healthy segments, epileptic seizure free segments and epileptic seizure segments. We showed that the proposed model resulted in satisfactory classification accuracy rates. © 2010 Elsevier Ltd. All rights reserved Daha fazlası Daha az

Özer, Mahmut | Perc, Matjaž | Uzuntarla, Muhammet

Makale | 2009 | EPL86 ( 4 ) , pp.13475 - 13481

We investigate the regularity of spontaneous spiking activity on Newman-Watts small-world networks consisting of biophysically realistic Hodgkin-Huxley neurons with a tunable intensity of intrinsic noise and fraction of blocked voltage-gated sodium and potassium ion channels embedded in neuronal membranes. We show that there exists an optimal fraction of shortcut links between physically distant neurons, as well as an optimal intensity of intrinsic noise, which warrant an optimally ordered spontaneous spiking activity. This doubly coherence resonance-like phenomenon depends significantly on, and can be controlled via, the fraction o . . .f closed sodium and potassium ion channels, whereby the impacts can be understood via the analysis of the firing rate function as well as the deterministic system dynamics. Potential biological implications of our findings for information propagation across neural networks are also discussed. © EPLA, 2009 Daha fazlası Daha az

Özer, Mahmut

Makale | 2004 | Iranian Journal of Science and Technology, Transaction B: Engineering28 ( 3 B ) , pp.351 - 358

In this study, the time-course of the recovery from inactivation of molluscan ionic currents is examined. Molluscan voltage-gated ionic currents are described in Hodgkin-Huxley-like equations. The peak value function of the recovering conductance is derived from the mathematical equivalent of an experimental procedure of the recovery process in a general form by including the number of inactivation gates. Then the curves of the recovery and its approximation for the molluscan ionic currents are obtained. It is shown that recovering conductance of molluscan ionic currents is asymptotically exponential. © Shiraz University.

Yılmaz, Ergin | Uzuntarla, Muhammet | Özer, Mahmut | Perc, Matjaž

Makale | 2013 | Physica A: Statistical Mechanics and its Applications392 ( 22 ) , pp.5735 - 5741

We study the phenomenon of stochastic resonance in a system of coupled neurons that are globally excited by a weak periodic input signal. We make the realistic assumption that the chemical and electrical synapses interact in the same neuronal network, hence constituting a hybrid network. By considering a hybrid coupling scheme embedded in the scale-free topology, we show that the electrical synapses are more efficient than chemical synapses in promoting the best correlation between the weak input signal and the response of the system. We also demonstrate that the average degree of neurons within the hybrid scale-free network signifi . . .cantly influences the optimal amount of noise for the occurrence of stochastic resonance, indicating that there also exists an optimal topology for the amplification of the response to the weak input signal. Lastly, we verify that the presented results are robust to variations of the system size. © 2013 Elsevier B.V. All rights reserved Daha fazlası Daha az

Baysal, Veli | Yılmaz, Ergin | Özer, Mahmut

Bildiri | 2015 | 2016 MEDICAL TECHNOLOGIES NATIONAL CONFERENCE (TIPTEKNO) , pp.5735 - 5741

In this paper, the effects of autapse (a kind of synapse formed between the axon or soma of a neuron and its own dendrite) on the transmission of weak signal are investigated in scale-free neuronal networks. In the study, we consider that each neuron in the network has an autapse modelled as chemical synapse. Besides, a subthreshold signal are injected to all neurons in the network. When obtained results are analyzed, it is seen that the autaptic conductance has a threshold value. According to this threshold, the effects of autapse on the transmission of weak signal are evaluated within two categories. When conductance of autapse is . . . less than this threshold value, autapses with proper autaptic time delay values slightly increase the transmission of weak signal. When autaptic conductance is bigger than the threshold value, autapses with proper autaptic time deley values prominently block the transmission of weak signal Daha fazlası Daha az