The Experts below are selected from a list of 150053343 Experts worldwide ranked by ideXlab platform
Toru Nishigami - One of the best experts on this subject based on the ideXlab platform.
-
2009 special issue an artificial chaotic spiking neuron inspired by spiral ganglion cell paralleled spike encoding theoretical analysis and electronic circuit implementation
Neural Networks, 2009Co-Authors: Hiroyuki Torikai, Toru NishigamiAbstract:A novel chaotic spiking neuron is presented and its nonlinear dynamics and encoding functions are analyzed. A set of paralleled N neurons accepts a common analog input and outputs a set of N chaotic spike-trains. Three theorems which guarantee that the neurons can encode the analog input into a summation of the N chaotic spike-trains are derived: (1) a spike histogram of the summed spike-train can mimic waveforms of various inputs, (2) the spike-trains do not synchronize to each other and thus the summed spike-train can have N times higher encoding resolution than each single spike-train, and (3) firing rates of the neurons can be adjusted by internal parameters. The theorems are proven by using nonlinear iterative maps and are confirmed by numerical simulations as well. Electronic circuit implementation methods of the paralleled neurons are also presented and typical paralleled encoding functions are confirmed by both experimental measurements and SPICE simulations.
-
an artificial chaotic spiking neuron inspired by spiral ganglion cell paralleled spike encoding theoretical analysis and electronic circuit implementation
International Joint Conference on Neural Network, 2009Co-Authors: Hiroyuki Torikai, Toru NishigamiAbstract:A novel chaotic spiking neuron is presented and its nonlinear dynamics and encoding functions are analyzed. A set of paralleled N neurons accepts a common analog input and outputs a set of N chaotic spike-trains. Three theorems which guarantee that the neurons can encode the analog input into a summation of the N chaotic spike-trains are derived: (1) a spike histogram of the summed spike-train can mimic waveforms of various inputs, (2) the spike-trains do not synchronize to each other and thus the summed spike-train can have N times higher encoding resolution than each single spike-train, and (3) firing rates of the neurons can be adjusted by internal parameters. The theorems are proven by using nonlinear iterative maps and are confirmed by numerical simulations as well. Electronic circuit implementation methods of the paralleled neurons are also presented and typical paralleled encoding functions are confirmed by both experimental measurements and SPICE simulations.
Hiroyuki Torikai - One of the best experts on this subject based on the ideXlab platform.
-
2009 special issue an artificial chaotic spiking neuron inspired by spiral ganglion cell paralleled spike encoding theoretical analysis and electronic circuit implementation
Neural Networks, 2009Co-Authors: Hiroyuki Torikai, Toru NishigamiAbstract:A novel chaotic spiking neuron is presented and its nonlinear dynamics and encoding functions are analyzed. A set of paralleled N neurons accepts a common analog input and outputs a set of N chaotic spike-trains. Three theorems which guarantee that the neurons can encode the analog input into a summation of the N chaotic spike-trains are derived: (1) a spike histogram of the summed spike-train can mimic waveforms of various inputs, (2) the spike-trains do not synchronize to each other and thus the summed spike-train can have N times higher encoding resolution than each single spike-train, and (3) firing rates of the neurons can be adjusted by internal parameters. The theorems are proven by using nonlinear iterative maps and are confirmed by numerical simulations as well. Electronic circuit implementation methods of the paralleled neurons are also presented and typical paralleled encoding functions are confirmed by both experimental measurements and SPICE simulations.
-
an artificial chaotic spiking neuron inspired by spiral ganglion cell paralleled spike encoding theoretical analysis and electronic circuit implementation
International Joint Conference on Neural Network, 2009Co-Authors: Hiroyuki Torikai, Toru NishigamiAbstract:A novel chaotic spiking neuron is presented and its nonlinear dynamics and encoding functions are analyzed. A set of paralleled N neurons accepts a common analog input and outputs a set of N chaotic spike-trains. Three theorems which guarantee that the neurons can encode the analog input into a summation of the N chaotic spike-trains are derived: (1) a spike histogram of the summed spike-train can mimic waveforms of various inputs, (2) the spike-trains do not synchronize to each other and thus the summed spike-train can have N times higher encoding resolution than each single spike-train, and (3) firing rates of the neurons can be adjusted by internal parameters. The theorems are proven by using nonlinear iterative maps and are confirmed by numerical simulations as well. Electronic circuit implementation methods of the paralleled neurons are also presented and typical paralleled encoding functions are confirmed by both experimental measurements and SPICE simulations.
Yoko Ohtsuka - One of the best experts on this subject based on the ideXlab platform.
-
characteristics of the synchronous occipital and frontopolar spike phenomenon in panayiotopoulos syndrome
Brain & Development, 2010Co-Authors: Harumi Yoshinaga, Katsuhiro Kobayashi, Yoko OhtsukaAbstract:Abstract Purpose: The synchronous appearance of an occipital and frontopolar spike (the Fp-O spike) is characteristic of Panayiotopoulos syndrome (PS). This phenomenon is also seen in various other types of epilepsy, particularly those that occur in childhood. Using dipole analysis and sequential mapping, we investigated the characteristics of the Fp-O spike observed in seven patients with PS and six patients with symptomatic localization-related epilepsy in childhood (SLE). Methods: We analyzed both one averaged spike and 20 manually selected successive individual Fp-O spikes for each patient through sequential topographical mapping with steps of 10 ms from 40 ms before to 40 ms after the negative maximum peak of each spike. For dipole analysis, a period of 40 ms before the maximum negative peak of the averaged spike in each patient was examined using equivalent current dipole localization software. Results: Sequential mapping revealed that occipital negative peaks preceded frontal negative peaks in all of the PS patients, as well as in two of the six SLE patients. The four remaining SLE patients did not exhibit preceding occipital peaks. In all of the patients with PS, representative dipole locations were in the posterior area, whereas in SLE patients they were scattered over more anterior areas. The estimated sources of the Fp-O and O spikes appeared to have the same position and orientation in the two PS patients. Conclusion: We conclude that Fp-O spikes in PS occur as the result of a rapid spread of epileptic activity from the posterior areas to the anterior areas of the brain. Fp-O spikes in PS patients show a uniform topographical pattern and dipole location, whereas those in other patients show more heterogeneity in these features. These findings support the homogeneity of PS and thus its designation as a syndrome.
-
dipole analysis in panayiotopoulos syndrome
Brain & Development, 2005Co-Authors: Harumi Yoshinaga, Atsushi Shirasawa, Kenichi Kikumoto, Michael Koutroumanidis, Yoko OhtsukaAbstract:Panayiotopoulos syndrome (PS) is a type of benign childhood partial epilepsy, which has a good prognosis despite the fact that it is frequently associated with abundant multifocal spikes on the electroencephalography (EEG). We investigated whether stable dipoles, as seen in rolandic epilepsy, were also present in PS. We performed dipole analysis of the interictal spike discharges seen in the interictal EEGs of eight children with PS. We chose more than 10 spikes for each kind of spike, and investigated whether or not more than three of these spikes showed consistently stable dipole locations. (1) We observed 15 different kinds of spikes in various regions in the EEGs of the eight children. (2) Twelve of the 15 kinds of spikes had dipoles with a high goodness of fit. Furthermore, 14 of the 15 spikes had stable dipoles with similar locations for more than three individual spikes. (3) Fourteen of the 15 spikes, including frontal spikes, showed dense dipole locations in the mesial occipital area. Thirteen of these 14 spikes also showed other dipole locations in the rolandic area and/or the vertex (Cz). Our study revealed that the various types of spikes observed in PS have similar and stable dipole locations. The dipoles showing high stability, were located in the mesial occipital area, and were accompanied by dipoles located in the rolandic area. The stability and location of these dipoles indicate that there may be a pathogenetic link between PS and rolandic epilepsy.
Katsuhiro Kobayashi - One of the best experts on this subject based on the ideXlab platform.
-
High-frequency oscillations in a spectrum of pediatric epilepsies characterized by sleep-activated spikes in scalp EEG
Clinical Neurophysiology, 2019Co-Authors: Yuji Ohuchi, Masao Matsuhashi, Tomoyuki Akiyama, Katsuhiro KobayashiAbstract:Abstract Objective We studied ripple-band (80–200 Hz) high-frequency oscillations in scalp electroencephalogram (EEG) in various pediatric epilepsies featuring sleep-activated spikes, such as epileptic encephalopathy with continuous Spike-and-Wave during sleep (CSWS) and investigated their characteristics. Methods The subjects were 94 children with epileptic disorders including idiopathic and non-idiopathic CSWS, benign epilepsy with centrotemporal spikes (BECTS), Panayiotopoulos syndrome, other types of focal epilepsies (oFE), and focal spikes without clinical seizures (Latent). We detected ripple oscillations using a semi-automatic detection tool based on localized power increase. Results In the idiopathic CSWS Group, the median ratio of ripples per spike in the initial EEG was 5.73, which was significantly higher than those in the BECTS, Panayiotopoulos syndrome, oFE, and Latent Groups (0.39, 0.02, 0.35, 0, respectively, all with p Conclusions This paper is the first to confirm a high ratio of ripples per spike in CSWS in the largest number of patients to date. Significance The dense generation of ripples, which occurs through a combination of heavy loading of individual spikes with ripples and large numbers of spikes during sleep, characterizes CSWS and might be closely related to the pathophysiology of this epileptic encephalopathy.
-
characteristics of the synchronous occipital and frontopolar spike phenomenon in panayiotopoulos syndrome
Brain & Development, 2010Co-Authors: Harumi Yoshinaga, Katsuhiro Kobayashi, Yoko OhtsukaAbstract:Abstract Purpose: The synchronous appearance of an occipital and frontopolar spike (the Fp-O spike) is characteristic of Panayiotopoulos syndrome (PS). This phenomenon is also seen in various other types of epilepsy, particularly those that occur in childhood. Using dipole analysis and sequential mapping, we investigated the characteristics of the Fp-O spike observed in seven patients with PS and six patients with symptomatic localization-related epilepsy in childhood (SLE). Methods: We analyzed both one averaged spike and 20 manually selected successive individual Fp-O spikes for each patient through sequential topographical mapping with steps of 10 ms from 40 ms before to 40 ms after the negative maximum peak of each spike. For dipole analysis, a period of 40 ms before the maximum negative peak of the averaged spike in each patient was examined using equivalent current dipole localization software. Results: Sequential mapping revealed that occipital negative peaks preceded frontal negative peaks in all of the PS patients, as well as in two of the six SLE patients. The four remaining SLE patients did not exhibit preceding occipital peaks. In all of the patients with PS, representative dipole locations were in the posterior area, whereas in SLE patients they were scattered over more anterior areas. The estimated sources of the Fp-O and O spikes appeared to have the same position and orientation in the two PS patients. Conclusion: We conclude that Fp-O spikes in PS occur as the result of a rapid spread of epileptic activity from the posterior areas to the anterior areas of the brain. Fp-O spikes in PS patients show a uniform topographical pattern and dipole location, whereas those in other patients show more heterogeneity in these features. These findings support the homogeneity of PS and thus its designation as a syndrome.
-
Clinical application of spike averaging to dipole tracing method
Brain Topography, 1993Co-Authors: Harumi Yoshinaga, Katsuhiro Kobayashi, Masahiro Sato, Michiko Mizukawa, Shunsuke OhtaharaAbstract:As part of our studies on localization of epileptic foci, dipole analysis using averaged spikes were compared with that using individual spikes for 25 patients with localization related epilepsy. Our results are as follows. 1) In the group which showed stable dipoles from individual spikes, dipole localization from averaged and individual spikes were similar, although the former showed a higher dipolarity and more stable location, for the entire spike discharge including the peak, trough and wave. The high dipolarity was due to improved signal to noise ratio obtained from averaging. 2) The cases with centrotemporal spike focus including benign childhood epilepsy with centrotemporal spikes showed more reliable dipoles. In the cases with frontal lobe epilepsy, reliable dipoles were rarely obtained even with averaged spikes. Each method provided independent information, so they are of complementary value.
Harumi Yoshinaga - One of the best experts on this subject based on the ideXlab platform.
-
characteristics of the synchronous occipital and frontopolar spike phenomenon in panayiotopoulos syndrome
Brain & Development, 2010Co-Authors: Harumi Yoshinaga, Katsuhiro Kobayashi, Yoko OhtsukaAbstract:Abstract Purpose: The synchronous appearance of an occipital and frontopolar spike (the Fp-O spike) is characteristic of Panayiotopoulos syndrome (PS). This phenomenon is also seen in various other types of epilepsy, particularly those that occur in childhood. Using dipole analysis and sequential mapping, we investigated the characteristics of the Fp-O spike observed in seven patients with PS and six patients with symptomatic localization-related epilepsy in childhood (SLE). Methods: We analyzed both one averaged spike and 20 manually selected successive individual Fp-O spikes for each patient through sequential topographical mapping with steps of 10 ms from 40 ms before to 40 ms after the negative maximum peak of each spike. For dipole analysis, a period of 40 ms before the maximum negative peak of the averaged spike in each patient was examined using equivalent current dipole localization software. Results: Sequential mapping revealed that occipital negative peaks preceded frontal negative peaks in all of the PS patients, as well as in two of the six SLE patients. The four remaining SLE patients did not exhibit preceding occipital peaks. In all of the patients with PS, representative dipole locations were in the posterior area, whereas in SLE patients they were scattered over more anterior areas. The estimated sources of the Fp-O and O spikes appeared to have the same position and orientation in the two PS patients. Conclusion: We conclude that Fp-O spikes in PS occur as the result of a rapid spread of epileptic activity from the posterior areas to the anterior areas of the brain. Fp-O spikes in PS patients show a uniform topographical pattern and dipole location, whereas those in other patients show more heterogeneity in these features. These findings support the homogeneity of PS and thus its designation as a syndrome.
-
dipole analysis in panayiotopoulos syndrome
Brain & Development, 2005Co-Authors: Harumi Yoshinaga, Atsushi Shirasawa, Kenichi Kikumoto, Michael Koutroumanidis, Yoko OhtsukaAbstract:Panayiotopoulos syndrome (PS) is a type of benign childhood partial epilepsy, which has a good prognosis despite the fact that it is frequently associated with abundant multifocal spikes on the electroencephalography (EEG). We investigated whether stable dipoles, as seen in rolandic epilepsy, were also present in PS. We performed dipole analysis of the interictal spike discharges seen in the interictal EEGs of eight children with PS. We chose more than 10 spikes for each kind of spike, and investigated whether or not more than three of these spikes showed consistently stable dipole locations. (1) We observed 15 different kinds of spikes in various regions in the EEGs of the eight children. (2) Twelve of the 15 kinds of spikes had dipoles with a high goodness of fit. Furthermore, 14 of the 15 spikes had stable dipoles with similar locations for more than three individual spikes. (3) Fourteen of the 15 spikes, including frontal spikes, showed dense dipole locations in the mesial occipital area. Thirteen of these 14 spikes also showed other dipole locations in the rolandic area and/or the vertex (Cz). Our study revealed that the various types of spikes observed in PS have similar and stable dipole locations. The dipoles showing high stability, were located in the mesial occipital area, and were accompanied by dipoles located in the rolandic area. The stability and location of these dipoles indicate that there may be a pathogenetic link between PS and rolandic epilepsy.
-
Clinical application of spike averaging to dipole tracing method
Brain Topography, 1993Co-Authors: Harumi Yoshinaga, Katsuhiro Kobayashi, Masahiro Sato, Michiko Mizukawa, Shunsuke OhtaharaAbstract:As part of our studies on localization of epileptic foci, dipole analysis using averaged spikes were compared with that using individual spikes for 25 patients with localization related epilepsy. Our results are as follows. 1) In the group which showed stable dipoles from individual spikes, dipole localization from averaged and individual spikes were similar, although the former showed a higher dipolarity and more stable location, for the entire spike discharge including the peak, trough and wave. The high dipolarity was due to improved signal to noise ratio obtained from averaging. 2) The cases with centrotemporal spike focus including benign childhood epilepsy with centrotemporal spikes showed more reliable dipoles. In the cases with frontal lobe epilepsy, reliable dipoles were rarely obtained even with averaged spikes. Each method provided independent information, so they are of complementary value.
