Considerations of quasi-stationarity in electrophysiological systems

Plonsey, Robert; Heppner, D. B.

doi:10.1007/bf02476917

Cited by 577 publications

(383 citation statements)

References 2 publications

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“…Assuming that the quasi-stationary approximation of the Maxwell equations provides a good description for the electrical activity reflected in EEG signals (Plonsey, 1967) volume-conducted electrical activity measured from two spatially separated sensors has zero (or negligible) delay (Stinstra, 1998). Therefore, a conservative strategy to avoid volume conduction effects is to exclude zero-lag inter-relationships (Nolte et al, 2004).…”

Section: Volume Conduction and Choice Of Referencementioning

confidence: 99%

Standing Waves as an Explanation for Generic Stationary Correlation Patterns in Noninvasive EEG of Focal Onset Seizures

et al. 2014

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Cerebral electrical activity is highly nonstationary because the brain reacts to ever changing external stimuli and continuously monitors internal control circuits. However, a large amount of energy is spent to maintain remarkably stationary activity patterns and functional inter-relations between different brain regions. Here we examine linear EEG correlations in the peri-ictal transition of focal onset seizures, which are typically understood to be manifestations of dramatically changing inter-relations. Contrary to expectations we find stable correlation patterns with a high similarity across different patients and different frequency bands. This skeleton of spatial correlations may be interpreted as a signature of standing waves of electrical brain activity constituting a dynamical ground state. Such a state could promote the formation of spatiotemporal neuronal assemblies and may be important for the integration of information stemming from different local circuits of the functional brain network.

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Section: Volume Conduction and Choice Of Referencementioning

confidence: 99%

Standing Waves as an Explanation for Generic Stationary Correlation Patterns in Noninvasive EEG of Focal Onset Seizures

et al. 2014

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“…There is evidence of anisotropic properties in head tissues (Hoeltzell & Dykes 1979); however, in this paper we shall consider only the isotropic case. The static approach for living tissues, which neglect displacement and eddy currents inside the head, was also assumed (Plonsey & Heppner 1967). The surface S j, jC1 is the boundary separating the inner and outer compartments R j and R jC1 .…”

Section: (D) Volume Conductor Modelmentioning

confidence: 99%

“…The EEG represents the voltage differences that these primary current sources produce between lead electrodes situated on the scalp. Unfortunately, the primary current sources yielded in differentiated locations inside the brain are blurred and mixed during the observation process, although the temporal structure of their dynamics is preserved due to the quasi-instantaneous propagation of the ohmic currents (Plonsey & Heppner 1967). In order to obtain a threedimensional reconstruction of the density of primary current sources extending along the whole cerebral volume from the EEG signals (only recorded by a few sensors), an inverse problem must be solved.…”

Section: Introductionmentioning

confidence: 99%

Fusing EEG and fMRI based on a bottom-up model: inferring activation and effective connectivity in neural masses

Riera

Aubert

Iwata

et al. 2005

Phil. Trans. R. Soc. B

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The elucidation of the complex machinery used by the human brain to segregate and integrate information while performing high cognitive functions is a subject of imminent future consequences. The most significant contributions to date in this field, known as cognitive neuroscience, have been achieved by using innovative neuroimaging techniques, such as electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI), which measure variations in both the time and the space of some interpretable physical magnitudes. Extraordinary maps of cerebral activation involving function-restricted brain areas, as well as graphs of the functional connectivity between them, have been obtained from EEG and fMRI data by solving some spatio-temporal inverse problems, which constitutes a top-down approach. However, in many cases, a natural bridge between these maps/graphs and the causal physiological processes is lacking, leading to some misunderstandings in their interpretation. Recent advances in the comprehension of the underlying physiological mechanisms associated with different cerebral scales have provided researchers with an excellent scenario to develop sophisticated biophysical models that permit an integration of these neuroimage modalities, which must share a common aetiology. This paper proposes a bottom-up approach, involving physiological parameters in a specific mesoscopic dynamic equations system. Further observation equations encapsulating the relationship between the mesostates and the EEG/f MRI data are obtained on the basis of the physical foundations of these techniques. A methodology for the estimation of parameters from fused EEG/fMRI data is also presented. In this context, the concepts of activation and effective connectivity are carefully revised. This new approach permits us to examine and discuss some future prospects for the integration of multimodal neuroimages.

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“…Considering the applied frequency and the dielectric properties of biological tissue, inductive processes can be neglected in the computation of the electric field strength and the electroquasistatic approximation derived from Maxwell's equations can be applied [7] with the electric potential , the angular frequency , the imaginary unit , the vacuum permittivity , the electric conductivity , and the relative permittivity of the model compartments.…”

Section: Finite Element Simulationmentioning

confidence: 99%

Numerical design studies on a novel electrostimulative osteosynthesis system for the mandible

Raben

Schmidt

Sridhar

et al. 2017

Current Directions in Biomedical Engineering

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Fractures or other major bone defects in the mandible are commonly treated by mounting a reconstruction plate at the fracture site. To avoid complications due to loosening of the implant or the fixation screws, electrical stimulation presents a possibility to accelerate bone healing. The aim of this study was to investigate different combinations of activated electrodes and plate designs regarding their feasibility for electrostimulation of the mandibular bone. The electric field distribution for multiple implant designs was computed using the finite element method. The results suggest that the electrode insulation renders a crucial parameter, which influences substantially the stimulation impact and its power consumption.

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Considerations of quasi-stationarity in electrophysiological systems

Cited by 577 publications

References 2 publications

Standing Waves as an Explanation for Generic Stationary Correlation Patterns in Noninvasive EEG of Focal Onset Seizures

Standing Waves as an Explanation for Generic Stationary Correlation Patterns in Noninvasive EEG of Focal Onset Seizures

Fusing EEG and fMRI based on a bottom-up model: inferring activation and effective connectivity in neural masses

Numerical design studies on a novel electrostimulative osteosynthesis system for the mandible

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