Ağaoğlu, Şükrüye Nihal | Özer, Mahmut | Çalım, Ali | Uzuntarla, Muhammet

Proceedings | 2017 | 2017 25th Signal Processing and Communications Applications Conference, SIU 2017

In this paper, the phenomena of Vibrational Resonance is investigated in an excitable system which consists of FitzHugh-Nagumo neurons with electrical coupling. Weak signal detection performance of excitable system is examined in scale-free network (unweighted or weighted) topology. The simulation results show that; weighting the scale-free network, average connectivity degree, amplitude and frequency of weak signal play an active role to determine the data carrying performance of neurons based on Vibrational Resonance. It is determined that, the amount of required energy for creating resonance peaks of excitable system is decreased . . . significantly by choosing the correct value of weight control parameter in a weighted network especially. © 2017 IEEE Daha fazlası Daha az

Çalım, Ali | Özer, Mahmut | Uzuntarla, Muhammet

Proceedings | 2017 | 2017 25th Signal Processing and Communications Applications Conference, SIU 2017

Nowadays, neurodegenerative diseases which affect human life quite negatively with motor, cognitive and psychiatric disorders are becoming widespread. One of the most common neurodegenerative disorder is Parkinson's disease. Recent electrophysiological experiments have shown that Basal Ganglia, a special region in the midbrain, is related to Parkinsonism. Beta frequency oscillations, which are important symptoms of Parkinson's disease, emerge intensively in Globus Pallidus and Subtalamus nuclei. In this study, anatomical connections of Globus Pallidus and Subtalamus are constructed computationally, and the cellular properties that g . . .ive rise to emergence of beta oscillations are investigated. © 2017 IEEE Daha fazlası Daha az

Çalım, Ali | Özer, Mahmut | Uzuntarla, Muhammet

Proceedings | 2018 | 26th IEEE Signal Processing and Communications Applications Conference, SIU 2018 , pp.1 - 4

Experimental and theoretical studies in recent years suggest that the first spike latency is an effective information carrier and contains more neural information than other spikes. Noise Delayed Decay (NDD) phenomenon emerges when the first spike latency of the neuron exposed to the periodic driving is maximum at a certain noise intensity interval. In this study, the latency dynamics of a single Hodgkin-Huxley neuron is investigated under periodic driving, background activity through dynamic synapses, and channel noise. The system response with first spike latency is investigated as a function of the presynaptic firing rate, the pa . . .rameter with an appropriate biophysical reality to control the level of activity in the nervous system. First, NDD behavior is investigated under suprathreshold stimulation in the presence of synapses at different levels of depression and channel noise. It is then desired to observe the NDD phenomenon under subthreshold stimulation with the same strategy. Our results have shown that the background activity occurring in the presence of dynamic synapses and the channel noise are significant system dynamics in observing the NDD behavior. © 2018 IEEE Daha fazlası Daha az

Çalım, Ali | Özer, Mahmut | Uzuntarla, Muhammet

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

Parkinson's disease is a neurodegenerative disorder that affect human life quite negatively with motor, cognitive and psychiatric way. Recent electrophysiological experiments have shown that Basal Ganglia, spaced in the midbrain, can lead to Parkinsonism. Beta frequency oscillations and irregular burstings are most important symptoms of Parkinson's disease. They appear in Globus Pallidus and Subtalamus nuclei during the disease. In this study, anatomical connection features that may give rise to emergence of burstings are investigated, simulating Globus Pallidus and Subtalamus nuclei numerically. © 2017 IEEE.

Çalım, Ali | Özer, Mahmut | Uzuntarla, Muhammet

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

In this study, vibrational resonance phenomena is investigated in excitable neuron population. Synapses where complex electrochemical events take place in is modelled dynamically, not statically by contrast with early studies. Effect of short-Term synaptic depression which is a prominent feature of dynamic synapses on vibrational resonance is studied. The results of numerical simulations that silencing effect of shortterm depression emerges in the cases where static synapses lead to vibrational resonance. © 2017 IEEE.

Çilli, Salih | Çalım, Ali | Uzuntarla, Muhammet

Proceedings | 2019 | TIPTEKNO 2019 - Tip Teknolojileri Kongresi , pp.1 - 4

Vital functions in living organisms occur through changes in electrical activity. These activities consist of brain rhythms with different frequencies that exhibit oscillatory behavior and can be monitored by local field potentials or EEG recordings. The synchronization of neural activity underlies the emergence of these rhythmic waves, which are of great importance in the nervous system. In this study, the effects of changes in intrinsic mechanisms and intercellular communication, that are constituting neural activity, on the synchronization of neuron pair which is composed of two nerve cells and connected with different types of s . . .ynaptic junction were investigated in a biologically meaningful way. The obtained results showed that the excitability, synaptic and ionic conductivity levels are crucial for neurons to synchronize. It has also been found that the noise caused by the stochastic nature of the ion channels is an auxiliary biological component to achieve synchronization. © 2019 IEEE Daha fazlası Daha az

Uzuntarla, Muhammet | Torres, Joaquin J. | Çalım, Ali | Barreto, Ernest

Article | 2019 | Neural Networks110 , pp.131 - 140

We observe and study a self-organized phenomenon whereby the activity in a network of spiking neurons spontaneously terminates. We consider different types of populations, consisting of bistable model neurons connected electrically by gap junctions, or by either excitatory or inhibitory synapses, in a scale-free connection topology. We find that strongly synchronized population spiking events lead to complete cessation of activity in excitatory networks, but not in gap junction or inhibitory networks. We identify the underlying mechanism responsible for this phenomenon by examining the particular shape of the excitatory postsynaptic . . . currents that arise in the neurons. We also examine the effects of the synaptic time constant, coupling strength, and channel noise on the occurrence of the phenomenon. © 2018 Elsevier Lt Daha fazlası Daha az

Çalım, Ali | Hövel, Philipp | Özer, Mahmut | Uzuntarla, Muhammet

Article | 2018 | Physical Review E98 ( 6 ) , pp.131 - 140

Chimeras are complex spatiotemporal patterns that emerge as coexistence of both coherent and incoherent groups of coupled dynamical systems. Here, we investigate the emergence of chimera states in nonlocal networks of type-I Morris-Lecar neurons coupled via chemical synapses. This constitutes a more realistic neuronal modeling framework than previous studies of chimera states, since the Morris-Lecar model provides biophysically more relevant control parameters to describe the activity in actual neural systems. We explore systematically the transitions of dynamic behavior and find that different types of synchrony appear depending on . . . the excitability level and nonlocal network features. Furthermore, we map the transitions between incoherent states, traveling waves, chimeras, coherent states, and global amplitude death in the parameter space of interest. This work contributes to a better understanding of biological conditions giving rise to the emergence of chimera states in neural medium. © 2018 American Physical Society Daha fazlası Daha az

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

Article | 2015 | Physical Review E - Statistical, Nonlinear, and Soft Matter Physics92 ( 6 ) , pp.131 - 140

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

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

Çalım, Ali | Özer, Mahmut | Uzuntarla, Muhammet

Proceedings | 2018 | 26th IEEE Signal Processing and Communications Applications Conference, SIU 2018 , pp.1 - 4

In this study, effects of the heterogeneity in neuronal networks and subthreshold signal features on subthreshold signal detection in the nervous system is investigated. 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 information processing performance of the neuron populations is systematically studied by using mathematical equations for modeling the dynamics of the neurons, which are basic units of the system. As a result of the simulations performed, it is seen . . . that the sub-threshold signal frequency and the heterogeneity in the excitability are important system parameters for optimizing the information encoding performance. It is shown that the population encoding performance is maximized depending on the subthreshold signal frequency at different optimum levels of heterogeneity in the population. © 2018 IEEE Daha fazlası Daha az

Ağaoğlu, Şükrüye Nihal | Çalım, Ali | Özer, Mahmut | Uzuntarla, Muhammet

Proceedings | 2017 | 2016 Medical Technologies National Conference, TIPTEKNO 2016 , pp.1 - 4

In this study, vibrational resonance phenomena is investigated for topologies of scale-free network in excitable neural system. Effect of heterogeneity which emerges from weightening synaptic conductivity in neural network on performance of weak signal detection is studied. FitzHugh-Nagumo neuron model with electrical coupling is used as excitable system. In the result of numerical simulations; it is seen that the state of the scale-free network being unweighted or weighted, synaptic conductivity and average connectivity degree play a crucial role for determining performance of information coding of neuron population based on vibrat . . .ional resonance. © 2016 IEEE Daha fazlası Daha az