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  • 1
    Electronic Resource
    Electronic Resource
    Time adaptive denoising of single trial event- related potentials in the wavelet domain (2000)
    Oxford, UK : Blackwell Publishing
    Psychophysiology 37 (2000), S. 0 
    Details
    ISSN: 1469-8986
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: We present a new wavelet-based method for single trial analysis of transient and time variant event-related potentials (ERPs). Expecting more accurate filter settings than achieved by other techniques (low-pass filter, a posteriori Wiener filter, time invariant wavelet filter), ERPs were initially balanced in time. By simulation, better filter performance could be established for test signals contaminated with either white noise or isospectral noise. To provide an example of real application, the method was applied to limbic P300 potentials (MTL-P300). As a result, variance of single trial MTL-P300s decreased, without restricting the corresponding mean. The proposed method can be regarded as an alternative for single-trial ERP analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1469-8986.3760859
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Seizure prediction by non-linear time series analysis of brain electrical activity (1998)
    Oxford, UK : Blackwell Science, Ltd
    European journal of neuroscience 10 (1998), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Brain electrical activity of 16 patients with temporal lobe epilepsy, recorded intracranially during seizure-free intervals as well as during transitions to the seizure state, was analysed using methods derived from the theory of non-linear dynamics. Long-lasting and marked changes towards low-dimensional system states were found to occur specifically up to 25 min prior to epileptic seizures and allow to predict the occurrence of individual seizures in time. These findings reflect a continuous increase in the degree of synchronicity, and thus open a window for the study of mechanisms generating seizures in humans. This offers new possibilities for therapeutic interventions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.1998.00090.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Methohexital-Induced Changes in Spectral Power of Neuromagnetic Signals: Beta Augmentation is Smaller Over the Hemisphere Containing the Epileptogenic Focus (1997)
    Springer
    Brain topography 10 (1997), S. 41-47 
    Details
    ISSN: 1573-6792
    Keywords: MEG ; EEG ; Methohexital ; Beta band activity ; Temporal lobe epilepsy ; Spectral analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Previous research has suggested that methohexital, a short-term barbiturate, alters activity in the primary epileptogenic area. It can be assumed that drug-induced activation of the epileptogenic focus provides a rapid and safe method to obtain a sufficient amount of information relevant for the lateralization and localisation of the primary epileptogenic area. This study shows that methohexital changes spectral power in the beta band derived from magnetoencephalographic (MEG) signals over the hemisphere ipsilateral to the primary epileptogenic area. This effect was demonstrated for 10/13 of the investigated patients suffering from unilateral temporal lobe epilepsy (TLE). The side and location of the primary epileptogenic area of these patients (5 left TLE, 8 right TLE) was determined invasively during presurgical evaluation. During a 1-2 minute interval after intravenous bolus injection of 100 mg methohexital a clear lateralization effect in the beta band was observed, which differed marginally between fronto-central, fronto-temporal and temporo-parietal brain regions. In addition, bilateral spectral power changes were obtained in the theta, alpha and gamma bands that differed between brain regions. Analyses of simultaneously recorded scalp electroencephalographic (EEG) data revealed effects consistent with those of the MEG analysis. The reduced enhancement of beta band spectral power of MEG recordings provides a potential application for the non-invasive lateralization of the primary epileptogenic area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022211007269
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Properties of Advanced Headmodelling and Source Reconstruction for the Localization of Epileptiform Activity (1998)
    Springer
    Brain topography 10 (1998), S. 283-290 
    Details
    ISSN: 1573-6792
    Keywords: Source localization ; Current density reconstruction ; Boundary-element-method ; Finite-element-method ; Temporal lobe epilepsy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract During the last decade multiple work has been done to determine the sources of epileptiform activity by means of dipole source localization based on recordings of the magnetoencephalogram (MEG) or the electroencephalogram (EEG). The actual available advanced volume conductor models and the multiple source reconstruction by regularization may give new impulse to EEG based source analyses in epilepsy patients. This study demonstrates the principal properties of these techniques. We applied two different EEG source reconstruction techniques within different volume conductor models to localize induced spike activity in a selected patient suffering from medically intractable temporal lobe epilepsy: 1) single moving dipole solution in a 3-shell spherical model versus individual head models (boundary-element-model, BEM, and finite-element-model, FEM); 2) a regularization technique for current density reconstructions using both BEM and FEM. When compared to findings of invasive recordings no adequate source locations were derived from the moving dipole solution in both the 3-shell head model and BEM. In contrast, a high congruence of source reconstruction and invasive determination of the focus was obtained using the regularization techniques in both BEM and FEM, indicating the high spatial accuracy of this technique in individual head models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022275024069
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    Paper (German National Licenses)
    Fulltext
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