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Enhancement of temporal coherence via time-periodic coupling strength in a scale-free network of stochastic Hodgkin-Huxley neurons

Yılmaz, Ergin | Baysal, Veli | Özer, Mahmut

Article | 2015 | Physics Letters, Section A: General, Atomic and Solid State Physics379 ( 26-27 ) , pp.1594 - 1599

We investigate the effects of time-periodic coupling strength on the temporal coherence or firing regularity of a scale-free network consisting of stochastic Hodgkin-Huxley (H-H) neurons. The temporal coherence exhibits a resonance-like behavior depending on the cell size or the channel noise intensity. The best temporal coherence requires an optimal channel noise intensity, and this coherence can be significantly increased by time-periodic coupling strength when its frequency matches the integer multiples of the intrinsic subthreshold oscillation frequency of H-H neuron. Particularly, we find the multiple-coherence resonance depend . . .ing on frequency of time-periodic coupling strength at the optimal noise intensity. We also obtain a resonance-like dependence of temporal coherence on the amplitude of time-periodic coupling strength. Additionally, we investigate the effects of average degree on the temporal coherence and find that the temporal coherence exhibits a resonance-like behavior with respect to the network average degree, indicating that the best regularity requires an optimal average degree. © 2015 Elsevier B.V. All rights reserved Daha fazlası Daha az

Visual tracking and control of Unmanned aerial vehicle İnsansız hava araçlarında görsel takip ve denetim

Surucu, Dilek | Surucu, Murat | Koksal, Kerem | Hacıoğlu, Rıfat

Proceedings | 2015 | 2015 23rd Signal Processing and Communications Applications Conference, SIU 2015 - Proceedings , pp.1849 - 1852

In this study, we perform target detection and tracking with Unmanned Aerial Vehicle (UAV) as well as the visual command of UAV. Our goal is to develop an autopilot system to reduce the human factor in UAV's. We create a system that follows different objects, stays locked to a graphical object which is glyph that has an encryption that only we describe, and executes the mission encoded on glyph in both indoor and outdoor tests. We obtain the targeting by the angle and the dimensions of the glyph. We've obtained successful results in applied presentations. © 2015 IEEE.

Detection of directional eye movements based on the electrooculogram signals through an artificial neural network

Erkaymaz, Hande | Özer, Mahmut | Orak, İlhami Muharrem

Article | 2015 | Chaos, Solitons and Fractals77 , pp.225 - 229

The electrooculogram signals are very important at extracting information about detection of directional eye movements. Therefore, in this study, we propose a new intelligent detection model involving an artificial neural network for the eye movements based on the electrooculogram signals. In addition to conventional eye movements, our model also involves the detection of tic and blinking of an eye. We extract only two features from the electrooculogram signals, and use them as inputs for a feed-forwarded artificial neural network. We develop a new approach to compute these two features, which we call it as a movement range. The res . . .ults suggest that the proposed model have a potential to become a new tool to determine the directional eye movements accurately. © 2015 Elsevier Ltd. All rights reserved Daha fazlası Daha az

Vibrational resonance in a heterogeneous scale free network of neurons

Uzuntarla, Muhammet | Yılmaz, Ergin | Wagemakers, Alexandre | Özer, Mahmut

Article | 2015 | Communications in Nonlinear Science and Numerical Simulation22 ( 01.Mar ) , pp.367 - 374

Vibrational resonance (VR) is a phenomenon whereby the response of some dynamical systems to a weak low-frequency signal can be maximized with the assistance of an optimal intensity of another high-frequency signal. In this paper, we study the VR in a heterogeneous neural system having a complex network topology. We consider a scale-free network of neurons where the heterogeneity is in the intrinsic excitability of the individual neurons. It is shown that emergence of VR in heterogeneous neuron population requires less energy than a homogeneous population. We also find that electrical coupling strength among neurons plays a key role . . . in determining the weak signal processing capacity of the heterogeneous population. Lastly, we investigate the influence of interneuronal link density on the VR and demonstrate that the energy needed to obtain the resonance grows with the increase in average degree. © 2014 Elsevier B.V Daha fazlası Daha az

Delayed feedback and detection of weak periodic signals in a stochastic Hodgkin-Huxley neuron

Yılmaz, Ergin | Özer, Mahmut

Article | 2015 | Physica A: Statistical Mechanics and its Applications421 , pp.455 - 462

We study the effect of the delayed feedback loop on the weak periodic signal detection performance of a stochastic Hodgkin-Huxley neuron. We consider an electrical autapse characterized by its coupling strength and delay time. The stochastic Hodgkin-Huxley neuron exhibits subthreshold oscillations, and thus has an intrinsic time scale with the subthreshold oscillations. Therefore, we investigate the interplay of the subthreshold oscillations, coupling strength and delay time on the weak periodic signal detection. Results indicate that the delayed feedback either enhances or suppresses the weak signal detection depending on its param . . .eters, when compared to that without the feedback. The delayed feedback augments the weak periodic signal detection for the optimal values of the intrinsic noise and the coupling strength when the delay time is close to the integer multiples of the period of the intrinsic oscillations, due to the multiple resonance among the weak signal, the intrinsic oscillations, and the delayed feedback. We analyze the interspike interval histograms and show that the delayed feedback enhances or suppresses the weak periodic signal detection by increasing or decreasing the phase locking (synchronization) between the spiking and the weak periodic signal. We also show that an optimal phase locking is obtained when the delay time is close to the period of the intrinsic oscillations, leading a single dominant time scale in the spike trains. © 2014 Elsevier B.V. All rights reserved Daha fazlası Daha az

The effect of channel blocking on first spike timing

Uzun, Rukiye | Özer, Mahmut


We investigate the first-spike response latency dynamics of a single Hodgkin-Huxley neuron model with a tunable intensity of intrinsic noise and fraction of blocked voltage-gated sodium and potassium ion channels embedded in biological membranes. In contrast to previous studies, we consider a biophysically realistic neuron model which contains stochastic ion channels. We show that potassium ion channels play a key role than sodium ion channels on the appearance of the noise delayed decay (NDD) effect in the first-spike timing.

EOG controlled direction detect system with neuro-fuzzy approach

Erkaymaz, Hande | Özer, Mahmut | Kaya, Ceren

Conference Object | 2015 | 2015 19TH NATIONAL BIOMEDICAL ENGINEERING MEETING (BIYOMUT) , pp.1191 - 1199

The eye, which has the most advanced features among sense organs, has a perfect functioning on people. Furthermore, as it is placed in the lead role of vision, shows the importance for people is quite big. Nowadays, biomedical devices developed for patients who have mobility are benefiting from eye movements. Electrooculogram studies are especially designed on the basis of the signal depending on the movement of your eyes. Electrical origin of EOG biological signal, that occur around the eye pupil, makes an attempt to meet the needs of patients by the right, left, up, down and blinking action. In this study, 4 basic differences exis . . .ting in the direction of movement using voltage controlled EOG signal studies have tried to determine the Neuro-Fuzzy model. Determining the direction of Neuro-Fuzzy control system demonstrates how it can be successfully used as. In addition, control algorithms of artificial intelligence systems that use this kind of eye signals benefiting from the input of the detection process is advantageous in the classification of complex environment Daha fazlası Daha az

Advances in renewable energy and energy efficiency technologies Preface

Çavdar, İsmail Hakkı | Suljanovic, Nermin | Uzuntarla, Muhammet


WOS: 000365508200001

Design of OFDM on digital signal processors

Emir, Ahmet | Kaya, Hakan | Öztürk, Ertan


In this work, Orthogonal Frequency Division Multiplexing (OFDM) is implemented on TMS320C6713 Digital Signal Processors (DSP) Starter Kit (DSK). Transmitter, receiver and communication channel are all implemented on a same kit. Firstly the design is tested within Matlab Simulink environment, and then by configuring C6713 DSK parameters, Simulink blocks relating to C6713 DSK are added into the design. The machine codes generated by compiling the design are loaded to the DSP kit. By comparing the voice signals generated via the simulation and the card, the obtained results are validated.

Effects of dynamic synapses on noise-delayed response latency of a single neuron

Uzuntarla, Muhammet | Özer, Mahmut | İleri, Uğur | Çalım, Ali | Torres, Joaquin J.

Article | 2015 | Physical Review E - Statistical, Nonlinear, and Soft Matter Physics92 ( 6 ) , pp.300 - 303

The noise-delayed decay (NDD) phenomenon emerges when the first-spike latency of a periodically forced stochastic neuron exhibits a maximum for a particular range of noise intensity. Here, we investigate the latency response dynamics of a single Hodgkin-Huxley neuron that is subject to both a suprathreshold periodic stimulus and a background activity arriving through dynamic synapses. We study the first-spike latency response as a function of the presynaptic firing rate f. This constitutes a more realistic scenario than previous works, since f provides a suitable biophysically realistic parameter to control the level of activity in . . .actual neural systems. We first report on the emergence of classical NDD behavior as a function of f for the limit of static synapses. Second, we show that when short-term depression and facilitation mechanisms are included at the synapses, different NDD features can be found due to their modulatory effect on synaptic current fluctuations. For example, an intriguing double NDD (DNDD) behavior occurs for different sets of relevant synaptic parameters. Moreover, depending on the balance between synaptic depression and synaptic facilitation, single NDD or DNDD can prevail, in such a way that synaptic facilitation favors the emergence of DNDD whereas synaptic depression favors the existence of single NDD. Here we report the existence of the DNDD effect in the response latency dynamics of a neuron. © 2015 American Physical Society Daha fazlası Daha az

The role of short-term synaptic depression and adaptive threshold on cortical irregular spike activity

İleri, Uğur | Çalım, Ali | Uzuntarla, Muhammet | Özer, Mahmut

Proceedings | 2015 | 2015 23rd Signal Processing and Communications Applications Conference, SIU 2015 - Proceedings , pp.1333 - 1336

In this study, the biophysical factors underlying the irregular spike patterns produced by neurons in the neocortex, whose cause and function are not fully understood yet, are investigated. In the experimental studies in the literature, it has been proposed that neocortical neurons are subject to high background activity. Thereby, the postsynaptic cortical neuron, used in the study, is modeled as a single-compartment neuron which receives random inputs from a large number of excitatory presynaptic neurons. Furthermore, synaptic transmission lines in the model are designed to include the short-term synaptic depression mechanism. In o . . .rder to examine the regularity of spike trains in postsynaptic neuron having fix and adaptive threshold, the coefficient of variation of interspikes intervals are computed. The obtained results show that short-term synaptic depression and adaptive threshold mechanisms might be candidate mechanisms explaining the irregular firings in cortical neurons. © 2015 IEEE Daha fazlası Daha az

EOG based intelligent direction detect system with pre-filtering algorithm

Erkaymaz, Hande | Özer, Mahmut | Kaya, Ceren | Orak, I. Muharrem


Nowadays, artificial movements have been obtained by utilizing other organs for paralyzed patients. Especially the usage of eye movements for giving message to outside world became popular as a scientific subject. In studies according to eye movements, the Electrooculogram (EOG) signal is used. In this study, the vertical and horizontal FOG signals taken from electrodes, placed around the eyes, have been modelled by using Artificial Neural Networks (ANN) which is one of artificial intelligent technique. The system can sense four main directions (Right, Left, Up and Down) at the same time it can also detect blinking movements. Firstl . . .y, the signals have been pre-filtered, amplified and classified by ANN. The performance of recommended model has been demonstrated by analyzing statistical accuracy and confusion matrix according to the features of obtained signal. It has been seen that eye movements can be successfully determined by designed model Daha fazlası Daha az

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