Proceedings of 16th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 1994
ABSTRACT Reports the use of EMG signals obtained from surface electrodes to determine the knee jo... more ABSTRACT Reports the use of EMG signals obtained from surface electrodes to determine the knee joint angle in paraplegic subjects, when the quadriceps muscle is electrically stimulated using percutaneous intramuscular electrodes. Isometric conditions at different fixed joint angles were considered. Both time domain and frequency domain analysis methods were used to characterize the EMG-joint angle relationship. The power spectrum of the EMG was estimated by a high resolution parametric method
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2008
The present paper concentrates on neural complexity generated during the phase transition in epil... more The present paper concentrates on neural complexity generated during the phase transition in epileptic seizure. Epileptic seizures represent a sudden and transient change in the synchronized firing of neuronal brain ensembles. The proposed model treats the brain as an excitable medium for the propagation of waves of electrical activity with a level of abstraction encompassing underlying variables into a number of discrete states. The analysis presented here provides support for the notion of dynamical phase transition in the sequence of chaos --> complexity --> order during the progress of epilepsy. Evolving cellular automata and quantifying it using Langton parameter shows critical value or highest complexity at the onset of seizure phenomenon.
ABSTRACT A one-dimensional map is proposed for modeling some of the neuronal activities, includin... more ABSTRACT A one-dimensional map is proposed for modeling some of the neuronal activities, including different spiking and bursting behaviors. The model is obtained by applying some modifications on the well-known Logistic map and is named the Modified and Confined Logistic (MCL) model. Map-based neuron models are known as phenomenological models and recently, they are widely applied in modeling tasks due to their computational efficacy. Most of discrete map-based models involve two variables representing the slow-fast prototype. There are also some one-dimensional maps, which can replicate some of the only specific neuronal activities. However, the existence of four bifurcation parameters in the MCL model gives rise to reproduction of spiking behavior with control over the frequency of the spikes, and imitation of chaotic and regular bursting responses concurrently. It is also shown that the proposed model has the potential to reproduce more realistic bursting activity by adding a second variable. Moreover the MCL model is able to replicate considerable number of experimentally observed neuronal responses introduced in (Izhikevich, 2004). Some analytical and numerical analyses of the MCL model dynamics are presented to explain the emersion of complex dynamics from this one-dimensional map. Keywords: map-based models; spiking and bursting patterns; bifurcation parameter; phenomenological models.
ABSTRACT This paper explores a computational dynamic solution for epileptic seizure control. A ne... more ABSTRACT This paper explores a computational dynamic solution for epileptic seizure control. A neuronal model of epileptiform activity which is driving to periodicity, simulating seizures, is chaotified via two chaos anti-control algorithms. Anti-control of some in vivo measurements is also put to test. The perspective is that in an epileptic disorder, a transition of the state of the neuronal system from being chaotic to being patho-physiologically periodic can cause this dynamical disorder. The aim is to retrieve the chaotic state which was running before the seizure start.Based on identifying loss regions for period orbits in the state space, the first control method acts by avoiding the system trajectories entrance into the defined loss regions. On the other hand, the second method, based on intra-attractor (orbit) control concept, is an attempt to steer trajectories to the unstable manifold of a target unstable period orbit solution embedded within the system dynamic. The presented anti-control methods make use of a novel strategy to model chaotic time series' return map with radial basis function to improve the estimation of the dynamics under investigation.Our results show that both methods are successful in driving the model's dynamical activity away from the periodic direction while the second one seems to be faster and more efficient. Moreover, testing both methods on some hippocampal recordings of epileptized rats yields fairly acceptable results in dynamic modulation. This opens ways for further online experimental stimulations based on chaos concept.
Abstract Neurofeedback training (NFT) has an important role in improvement of cognitive functions... more Abstract Neurofeedback training (NFT) has an important role in improvement of cognitive functions in both clinical and healthy individuals. In this study, variation of wavelet entropy during low beta NFT was investigated. To investigate the effect of low beta NFT on wavelet entropy, correlation between the change in low beta activity and the change in wavelet entropy was computed. The results revealed that there is a highly significant negative correlation between the change in low beta activity and wavelet entropy. The given ...
Skip to Main Content. IEEE.org | IEEE Xplore Digital Library | IEEE Standards Association | Spect... more Skip to Main Content. IEEE.org | IEEE Xplore Digital Library | IEEE Standards Association | Spectrum Online | More IEEE Sites. IEEE Xplore Digital Library. Search Term(s). Advanced Search | Preferences | Search Tips. ...
The Australian and New Zealand journal of psychiatry, 2016
In the absence of a comprehensive neural model to explain the underlying mechanisms of disturbed ... more In the absence of a comprehensive neural model to explain the underlying mechanisms of disturbed circadian function in bipolar disorder, mathematical modeling is a helpful tool. Here, circadian activity as a response to exogenous daily cycles is proposed to be the product of interactions between neuronal networks in cortical (cognitive processing) and subcortical (pacemaker) areas of the brain. To investigate the dynamical aspects of the link between disturbed circadian activity rhythms and abnormalities of neurotransmitter functioning in frontal areas of the brain, we developed a novel mathematical model of a chaotic system which represents fluctuations in circadian activity in bipolar disorder as changes in the model's parameters. A novel map-based chaotic system was developed to capture disturbances in circadian activity across the two extreme mood states of bipolar disorder. The model uses chaos theory to characterize interplay between neurotransmitter functions and rhythm g...
Proceedings of 16th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 1994
ABSTRACT Reports the use of EMG signals obtained from surface electrodes to determine the knee jo... more ABSTRACT Reports the use of EMG signals obtained from surface electrodes to determine the knee joint angle in paraplegic subjects, when the quadriceps muscle is electrically stimulated using percutaneous intramuscular electrodes. Isometric conditions at different fixed joint angles were considered. Both time domain and frequency domain analysis methods were used to characterize the EMG-joint angle relationship. The power spectrum of the EMG was estimated by a high resolution parametric method
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2008
The present paper concentrates on neural complexity generated during the phase transition in epil... more The present paper concentrates on neural complexity generated during the phase transition in epileptic seizure. Epileptic seizures represent a sudden and transient change in the synchronized firing of neuronal brain ensembles. The proposed model treats the brain as an excitable medium for the propagation of waves of electrical activity with a level of abstraction encompassing underlying variables into a number of discrete states. The analysis presented here provides support for the notion of dynamical phase transition in the sequence of chaos --> complexity --> order during the progress of epilepsy. Evolving cellular automata and quantifying it using Langton parameter shows critical value or highest complexity at the onset of seizure phenomenon.
ABSTRACT A one-dimensional map is proposed for modeling some of the neuronal activities, includin... more ABSTRACT A one-dimensional map is proposed for modeling some of the neuronal activities, including different spiking and bursting behaviors. The model is obtained by applying some modifications on the well-known Logistic map and is named the Modified and Confined Logistic (MCL) model. Map-based neuron models are known as phenomenological models and recently, they are widely applied in modeling tasks due to their computational efficacy. Most of discrete map-based models involve two variables representing the slow-fast prototype. There are also some one-dimensional maps, which can replicate some of the only specific neuronal activities. However, the existence of four bifurcation parameters in the MCL model gives rise to reproduction of spiking behavior with control over the frequency of the spikes, and imitation of chaotic and regular bursting responses concurrently. It is also shown that the proposed model has the potential to reproduce more realistic bursting activity by adding a second variable. Moreover the MCL model is able to replicate considerable number of experimentally observed neuronal responses introduced in (Izhikevich, 2004). Some analytical and numerical analyses of the MCL model dynamics are presented to explain the emersion of complex dynamics from this one-dimensional map. Keywords: map-based models; spiking and bursting patterns; bifurcation parameter; phenomenological models.
ABSTRACT This paper explores a computational dynamic solution for epileptic seizure control. A ne... more ABSTRACT This paper explores a computational dynamic solution for epileptic seizure control. A neuronal model of epileptiform activity which is driving to periodicity, simulating seizures, is chaotified via two chaos anti-control algorithms. Anti-control of some in vivo measurements is also put to test. The perspective is that in an epileptic disorder, a transition of the state of the neuronal system from being chaotic to being patho-physiologically periodic can cause this dynamical disorder. The aim is to retrieve the chaotic state which was running before the seizure start.Based on identifying loss regions for period orbits in the state space, the first control method acts by avoiding the system trajectories entrance into the defined loss regions. On the other hand, the second method, based on intra-attractor (orbit) control concept, is an attempt to steer trajectories to the unstable manifold of a target unstable period orbit solution embedded within the system dynamic. The presented anti-control methods make use of a novel strategy to model chaotic time series' return map with radial basis function to improve the estimation of the dynamics under investigation.Our results show that both methods are successful in driving the model's dynamical activity away from the periodic direction while the second one seems to be faster and more efficient. Moreover, testing both methods on some hippocampal recordings of epileptized rats yields fairly acceptable results in dynamic modulation. This opens ways for further online experimental stimulations based on chaos concept.
Abstract Neurofeedback training (NFT) has an important role in improvement of cognitive functions... more Abstract Neurofeedback training (NFT) has an important role in improvement of cognitive functions in both clinical and healthy individuals. In this study, variation of wavelet entropy during low beta NFT was investigated. To investigate the effect of low beta NFT on wavelet entropy, correlation between the change in low beta activity and the change in wavelet entropy was computed. The results revealed that there is a highly significant negative correlation between the change in low beta activity and wavelet entropy. The given ...
Skip to Main Content. IEEE.org | IEEE Xplore Digital Library | IEEE Standards Association | Spect... more Skip to Main Content. IEEE.org | IEEE Xplore Digital Library | IEEE Standards Association | Spectrum Online | More IEEE Sites. IEEE Xplore Digital Library. Search Term(s). Advanced Search | Preferences | Search Tips. ...
The Australian and New Zealand journal of psychiatry, 2016
In the absence of a comprehensive neural model to explain the underlying mechanisms of disturbed ... more In the absence of a comprehensive neural model to explain the underlying mechanisms of disturbed circadian function in bipolar disorder, mathematical modeling is a helpful tool. Here, circadian activity as a response to exogenous daily cycles is proposed to be the product of interactions between neuronal networks in cortical (cognitive processing) and subcortical (pacemaker) areas of the brain. To investigate the dynamical aspects of the link between disturbed circadian activity rhythms and abnormalities of neurotransmitter functioning in frontal areas of the brain, we developed a novel mathematical model of a chaotic system which represents fluctuations in circadian activity in bipolar disorder as changes in the model's parameters. A novel map-based chaotic system was developed to capture disturbances in circadian activity across the two extreme mood states of bipolar disorder. The model uses chaos theory to characterize interplay between neurotransmitter functions and rhythm g...
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