Baysal, Veli | Özer, Mahmut | Yılmaz, Ergin

Proceedings | 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.

Baysal, Veli | Yılmaz, Ergin | Özer, Mahmut

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

In this paper, the effects of autapse on the first spike latency of the stochastic H-H neuron are examined. In the study, it is considered that H-H neuron has an electrical autapse and by applying a suprathreshold periodic signal to neuron the first spike times has been observed. Obtained results show that the first spike latency of H-H neuron increases prominently in a certain autaptic time delay with the increasing of autaptic conductance. Also, the first spike latency decreases with the increasing of autaptic conductance in a different autaptic time delay interval. In the context of these results, we come to conclusion that the a . . .utapse have played important roles on the control of first spike latency of stochastic H-H neurons. © 2017 IEEE Daha fazlası Daha az

Öztürk, Ertan | Yılmaz, Ergin

Proceedings | 2007 | MobiWac'07 - Proceedings of the 5th ACM International Workshop on Mobility Management and Wireless Access , pp.107 - 111

In this paper, we investigate the probability of error performance of Direct Sequence Ultra Wide Band (DS-UWB) signals using various pulse shapes over the CM1 model of the Standard UWB channel. The considered pulse shapes are the first and second derivatives of Gauss waveform, Rayleigh waveform, and first four orthogonal modified Hermite waveforms. Results reveals that the probability of errors for all available pulse shapes over the considered channel are very similar for few users. However, by increasing the number of users, the performance differences start to appear in favor of Hermite pulses. © 2007 ACM.

Öztürk, Ertan | Yılmaz, Ergin

Proceedings | 2007 | 2007 IEEE 15th Signal Processing and Communications Applications, SIU , pp.107 - 111

In this paper, the probabilities of error performances of bipolar Direct Sequence Ultra Wide Band (DS-UWB) signals are investigated over a log-normal fading channel. Since the bandwidth of UWB signals is in the level of giga Hertz, the number of the resolvable paths in the channel is large. Consequently, in the receiver, a Rake receiver in conjunction with a maximum ratio combiner is used. By using the derived probability of error expression, the numerical values of the performances are calculated for the first derivative of Gaussian, the second derivative of Gaussian, Rayleigh and Daubechies-5 (db-5) pulse signals. Results show tha . . .t the db-5 pulse based UWB system gives the best performance Daha fazlası Daha az

Erkan, Yasemin | Özer, Mahmut | Yılmaz, Ergin

Proceedings | 2017 | 2017 MEDICAL TECHNOLOGIES NATIONAL CONGRESS (TIPTEKNO) , pp.107 - 111

Astrocytes are star-shaped glia cells and the most common cell type in the human brain with neurons. Astrocytes fulfill many functions in human brain. Providing support to the cells of the blood-brain barrier, balancing the extracellular ion concentration, supplying nutrients to the nerve tissue, and controlling the development of nerve cells are some of these tasks. In this study, the effects of calcium (Ca') ion concentration oscillations occuring in astrocytes on the neuron firing dynamics are investigated. When the obtained results are examined, it is observed that the production rate of insole 1,4,5-triphosphate (IP3), which is . . . an agent that triggers calcium release from the resoruces in astrocytes, and the degradation time of that within the cell are important effects on the spike production dynamics of the neuron in contact with astrocyte. It is determined that neurons without any stimulation continue to produce spikes through calcium oscillations in the astrocytes, at high IP3 production rates and longer IP3 degradation times Daha fazlası Daha az

Yılmaz, Ergin | Baysal, Veli | Özer, Mahmut

Proceedings | 2016 | 2016 24th Signal Processing and Communication Application Conference, SIU 2016 - Proceedings , pp.2233 - 2236

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 firing regularity and the firing rate in single Hodgkin-Huxley neuron are investigated. We consider that Hodgkin-Huxley neuron has two autapses. It is supposed that one of them is electrical synapse and the other is chemical synapse. Obtained results indicate that autapse with proper parameter values (delay time and autaptic conductance) prominently increases the firing regularity and the firing rate of a Hodgkin-Huxley neuron. © 2016 IEEE.

Yılmaz, Ergin | Baysal, Veli | Özer, Mahmut

Proceedings | 2015 | 2015 23rd Signal Processing and Communications Applications Conference, SIU 2015 - Proceedings , pp.1114 - 1117

In this paper, the effects of high-frequency driving on the weak signal detection capacity of Hodgkin-Huxley neuron are investigated. It is seen that the response of Hodgkin-Huxley neuron shows vibrational resonance with respect to the amplitude of high-frequency driving, and the best detection is obtained at an optimal amplitude of high-frequency driving. Besides, the effects of the frequency of high-frequency driving on the vibrational resonance are investigated. We arrived at the result that resonant response of the neuron can also be obtained for different frequencies of high-frequency signal but larger amplitudes are required f . . .or greater frequency of high frequency signal. © 2015 IEEE Daha fazlası Daha az

Erkan, Yasemin | Özer, Mahmut | Yılmaz, Ergin

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

Astrocytes are star-shaped glia cells and the most common cell type in the human brain with neurons. Astrocytes fulfill many functions in human brain. Providing support to the cells of the blood-brain barrier, balancing the extracellular ion concentration, supplying nutrients to the nerve tissue, and controlling the development of nerve cells are some of these tasks. In this study, the effects of calcium (Ca2+) ion concentration oscillations occuring in astrocytes on the neuron firing dynamics are investigated. When the obtained results are examined, it is observed that the production rate of insole 1,4,5-Triphosphate (IP3), which i . . .s an agent that triggers calcium release from the resoruces in astrocytes, and the degradation time of that within the cell are important effects on the spike production dynamics of the neuron in contact with astrocyte. It is determined that neurons without any stimulation continue to produce spikes through calcium oscillations in the astrocytes, at high IP3 production rates and longer IP3 degradation times. © 2017 IEEE Daha fazlası Daha az

Yılmaz, Ergin | Özer, Mahmut | Çavuşoğlu, Abdullah

Proceedings | 2011 | INISTA 2011 - 2011 International Symposium on INnovations in Intelligent SysTems and Applications , pp.581 - 584

The channel noise stemming from voltage-gated ion channels, which embedded in excitable neuronal membranes has a great impact on the production and propagation of the action potential in stochastic Hodgkin-Huxley (HH) neurons. In this study, we investigate the effects of sodium and potassium channels blockage and the average degree of connectivity on the spontaneous collective firing regularity on scale-free network which consisting of stochastic HH neurons. The obtained results reveal that potassium channel blockage has constructive effects on the firing regularity whereas sodium channel blockage has disruptive effects on the firin . . .g regularity. On the other hand, the spontaneous firing regularity exhibits coherence resonance depending on both the channel blockage scaling factor and the neuronal membrane area. The results also indicate that there is a lower boundary for the average degree of the network connectivity where the coherence resonance exists when the value of the network connectivity is greater than this lower boundary. © 2011 IEEE Daha fazlası Daha az

Baysal, Veli | Yılmaz, Ergin | Özer, Mahmut

Proceedings | 2015 |

n 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 transmission of weak localized rhythmic activity are investigated depending on ion channel noise in a Newman-Watts small-word networks of stochastic Hodgkin-huxley neurons. In this study, we consider that only a neuron, called pacemaker, to which a weak periodic stimuli is injected has an autapse. Obtained results indicate that autapse with proper parameter values (delay time and coupling strength) prominently increases the transmission of weak localized rhythmic activity across the network as compared to . . . the case in which pacemaker neuron does not have the autapse. Besides, we find that autapse can significantly enhances the transmission of weak local activity for different network topologies having different p values Daha fazlası Daha az

Baysal, Veli | Yılmaz, Ergin | Özer, Mahmut

Proceedings | 2015 | 2016 MEDICAL TECHNOLOGIES NATIONAL CONFERENCE (TIPTEKNO) , pp.581 - 584

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

Baysal, Veli | Yılmaz, Ergin | Özer, Mahmut

Proceedings | 2014 | 2014 22nd Signal Processing and Communications Applications Conference, SIU 2014 - Proceedings , pp.1958 - 1961

In this paper, the effects of time-periodic coupling on the firing regularity of a scale-free network (SF), consisting of stochastic Hodgkin-Huxley neurons, have been investigated depending on ion channel noise. The effects of both the frequency and the amplitude of periodic coupling on the firing regularity have been tackled, separately. It is seen from the obtained results that the firing (spiking) regularity shows resonance like behavior depending on ion channel noise when the frequency of the periodic coupling equals integer multiple of the sub threshold oscillation frequency of H-H neurons. Additionally, it is determined that t . . .his resonance is maximal at an optimal value of the amplitude of the periodic coupling strength. © 2014 IEEE Daha fazlası Daha az