On time delay estimation of epileptic EEG

Harris, Bernard; Gath, Isak; Rondouin, G.; Feuerstein, Claude

doi:10.1109/10.312089

Cited by 29 publications

(11 citation statements)

References 23 publications

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“…Volume conduction of the seizure EEG through the extracellular medium can account for high signal coherences between two regions despite lack of neuronal conduction. Thus signal coherence between structures may be high, yet not derived from direct synaptic connections (21,23,24). Another misleading scenario is that of a common pacemaker center, synapsing with AN as well as other regions including cortex (CTX).…”

mentioning

confidence: 99%

Anterior Thalamic Mediation of Experimental Seizures: Selective EEG Spectral Coherence

Mirski

Tsai

Rossell³

et al. 2003

Epilepsia

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Summary:Purpose: Physiological evidence has shown that the anterior thalamus (AN) and its associated efferents/ afferents constitute an important propagation pathway for pentylenetetrazol (PTZ)-mediated generalized seizures in rodents. Previous work demonstrated metabolic, physical, chemical, and electrical stimulation data supporting a role for AN in the expression of PTZ seizures. We now extend these observations through examination of neuroelectric signal indicators during seizure epochs. We show that the EEG recorded from AN is highly coherent with surface cortical (CTX) EEG during the immediate preconvulsant period and during the ictal stateough.Methods: Awake rats were continuously infused with PTZ until clonic seizures were recorded by using both subcortical AN, posterior thalamus (PT), or hippocampal (HPC) bipolar electrodes and cortical EEG. Through the signal-analysis techniques of ordinary and partial coherence, it was possible to focus selectively on signal correlations between AN and CTX (AN/CTX) by removing the effects of unaffiliated regions such as PT and HPC.Results: Coherence of PT/CTX was observed to be modest, and partial coherence of PT/CTX with the effects of AN/CTX removed did not improve the signal coherence of PT/CTX (PT/ CTX-AN). In contrast, AN/CTX coherence was observed to be high, with undiminished correlation when PT/CTX influence was removed (AN/CTX-PT). The most robust band of AN/ CTX coherence was centered around the spike-wave clonic frequency of 1-3 Hz. Partial multiple coherence-analysis techniques were used to remove the possible signal contributions from hippocampus in addition to PT. The AN/CTX coherence remained fully preserved in the low-frequency bands.Conclusions: These data provide electrophysiologic evidence supporting the special role of the anterior thalamus in the propagation of seizure activity between subcortex and cortex. Key Words: Anterior thalamus-EEG-Coherence-Seizure-Pentylenetetrazol.The precise neuronal pathways underlying the propagation and generalization of epileptic seizure activity remain largely unknown (1-6). Numerous studies have been performed to analyze the electrophysiology of focal cortical and hippocampal epileptic foci, and the local spread of these electrical paroxysms (7-10). Identification of specific cortical-subcortical pathways mediating seizure propagation between deep and surface neuronal elements has yet remained elusive, despite studies supporting the contribution of deep brain regions in clinical and EEG seizure expression (1-6). Mapping such connectivity would greatly improve our understanding of seizure mechanisms on a systems level, and offer potential sites for target-specific therapy, such as deep brain stimulation.Previously we established that the thalamic anterior nuclear complex (AN), a thalamic element of the limbic system, is an important gating center for the propagation of pentylenetetrazol (PTZ) seizure activity (11-15). Experiments supporting the hypothesis of AN mediation of convulsive activity include selective up...

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mentioning

confidence: 99%

Anterior Thalamic Mediation of Experimental Seizures: Selective EEG Spectral Coherence

Mirski

Tsai

Rossell³

et al. 2003

Epilepsia

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“…For coherence estimates, for example, the bias factor is reduced to k/m, and the variance becomes approximately (k/m) 2 , where k is again the order of the model and m the number of time samples (129). Similarly, multichannel AR algorithms yield superior estimates of time delays in rapidly changing dynamic systems (120). This appears to open up significant new possibilities for single-trial correlation of EEG patterns with human psychophysical or cognitive responses (48,129,134).…”

Section: Complex Multivariate Analysis Based On Multichannel Parametrmentioning

confidence: 96%

A General Statistical Framework for Frequency-Domain Analysis of EEG Topographic Structure

Kelly

Lenz

Franaszczuk

et al. 1997

Computers and Biomedical Research

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“…Once the optimum weight vector for that specific is obtained, the procedure is repeated by updating using the LM algorithm [15]. For the time-delay adaptation, the goal is to iteratively find the necessary changes for that lead to the minimum of the cost function (9) using the following adaptation rule (10) where is the iteration index and is the updating step. The updating step can be generated using different nonlinear adaptation approaches such as the steepest descent method, which converges linearly and may be inefficient, particularly as the minimum is approached, or the Newtons method which converges quadratically provided that an adequate initial estimate of the unknown weight vector is available [15].…”

Section: B Time-delay Adaptation Processmentioning

confidence: 99%

“…The first step deals with the timedelay estimation (TDE) between the two sequences while the second step deals with the interference cancellation. TDE is needed not only for interference-cancellation type problems, but also for source localization, direction of arrival estimation, etc., [10], [11]. Several methods have been developed for TDE, but the problem is still a subject of extensive research, since delay estimation becomes very difficult in real-life situations.…”

mentioning

confidence: 99%

Interference cancellation in respiratory sounds via a multiresolution joint time-delay and signal-estimation scheme

Charleston

Azimi-Sadjadi²,

González-Camarena³

1997

IEEE Trans. Biomed. Eng.

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Abstract-This paper is concerned with the problem of cancellation of heart sounds from the acquired respiratory sounds using a new joint time-delay and signal-estimation (JTDSE) procedure. Multiresolution discrete wavelet transform (DWT) is first applied to decompose the signals into several subbands. To accurately separate the heart sounds from the acquired respiratory sounds, time-delay estimation (TDE) is performed iteratively in each subband using two adaptation mechanisms that minimize the sum of squared errors between these signals. The time delay is updated using a nonlinear adaptation, namely the Levenberg-Marquardt (LM) algorithm, while the function of the other adaptive system-which uses the block fast transversal filter (BFTF)-is to minimize the mean squared error between the outputs of the delay estimator and the adaptive filter. The proposed methodology possesses a number of key benefits such as the incorporation of multiple complementary information at different subbands, robustness in presence of noise, and accuracy in TDE. The scheme is applied to several cases of simulated and actual respiratory sounds under different conditions and the results are compared with those of the standard adaptive filtering. The results showed the promise of the scheme for the TDE and subsequent interference cancellation.

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On time delay estimation of epileptic EEG

Cited by 29 publications

References 23 publications

Anterior Thalamic Mediation of Experimental Seizures: Selective EEG Spectral Coherence

Anterior Thalamic Mediation of Experimental Seizures: Selective EEG Spectral Coherence

A General Statistical Framework for Frequency-Domain Analysis of EEG Topographic Structure

Interference cancellation in respiratory sounds via a multiresolution joint time-delay and signal-estimation scheme

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