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Realistic and spherical head modeling for EEG forward problem solution: a comparative cortex-based analysis.

Vatta F, Meneghini F, Esposito F, Mininel S, Di Salle F - Comput Intell Neurosci (2010)

Bottom Line: In this paper we compare different spherical and realistic head modeling techniques in estimating EEG forward solutions from current dipole sources distributed on a standard cortical space reconstructed from Montreal Neurological Institute (MNI) MRI data.Computer simulations are presented for three different four-shell head models, two with realistic geometry, either surface-based (BEM) or volume-based (FDM), and the corresponding sensor-fitted spherical-shaped model.Realistic geometry turns out to be a relevant factor of improvement, particularly important when considering sources placed in the temporal or in the occipital cortex.

View Article: PubMed Central - PubMed

Affiliation: DEEI, University of Trieste, Via A. Valerio 10, 34127 Trieste, Italy. federica.vatta@deei.units.it

ABSTRACT
The accuracy of forward models for electroencephalography (EEG) partly depends on head tissues geometry and strongly affects the reliability of the source reconstruction process, but it is not yet clear which brain regions are more sensitive to the choice of different model geometry. In this paper we compare different spherical and realistic head modeling techniques in estimating EEG forward solutions from current dipole sources distributed on a standard cortical space reconstructed from Montreal Neurological Institute (MNI) MRI data. Computer simulations are presented for three different four-shell head models, two with realistic geometry, either surface-based (BEM) or volume-based (FDM), and the corresponding sensor-fitted spherical-shaped model. Point Spread Function (PSF) and Lead Field (LF) cross-correlation analyses were performed for 26 symmetric dipole sources to quantitatively assess models' accuracy in EEG source reconstruction. Realistic geometry turns out to be a relevant factor of improvement, particularly important when considering sources placed in the temporal or in the occipital cortex.

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The simulated 26 cortical sources in the Talairach coordinate system.
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Related In: Results  -  Collection


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fig4: The simulated 26 cortical sources in the Talairach coordinate system.

Mentions: The sources used for the simulation study are shown in Figure 4. In detail, 5000 evenly spaced points on the brain cortex mesh were initially considered as possible source positions while 26 “true” source positions have been placed in specific vertices of this mesh. The 26 source positions have been selected in order to achieve a rather uniform spatial sampling of the source space, with the aim of investigating the main differences that can be observed in terms of source reconstruction for the various cortical regions in the spherically approximated and in the two different superficial- and volume-based realistic models. For each source position, three single dipole sources have been placed, oriented parallel to the x, y, or z orthogonal Cartesian axes according to the “Talairach” coordinate system, since a source with generic orientation can be always decomposed in its components along the coordinate axes [6]. The study was performed using the numerical FDM for EEG forward problem solution presented in [10], the Galerkin BEM with linear basis algorithm described in [7] for BEM, and analytic calculations for the spherical model [7].


Realistic and spherical head modeling for EEG forward problem solution: a comparative cortex-based analysis.

Vatta F, Meneghini F, Esposito F, Mininel S, Di Salle F - Comput Intell Neurosci (2010)

The simulated 26 cortical sources in the Talairach coordinate system.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2821797&req=5

fig4: The simulated 26 cortical sources in the Talairach coordinate system.
Mentions: The sources used for the simulation study are shown in Figure 4. In detail, 5000 evenly spaced points on the brain cortex mesh were initially considered as possible source positions while 26 “true” source positions have been placed in specific vertices of this mesh. The 26 source positions have been selected in order to achieve a rather uniform spatial sampling of the source space, with the aim of investigating the main differences that can be observed in terms of source reconstruction for the various cortical regions in the spherically approximated and in the two different superficial- and volume-based realistic models. For each source position, three single dipole sources have been placed, oriented parallel to the x, y, or z orthogonal Cartesian axes according to the “Talairach” coordinate system, since a source with generic orientation can be always decomposed in its components along the coordinate axes [6]. The study was performed using the numerical FDM for EEG forward problem solution presented in [10], the Galerkin BEM with linear basis algorithm described in [7] for BEM, and analytic calculations for the spherical model [7].

Bottom Line: In this paper we compare different spherical and realistic head modeling techniques in estimating EEG forward solutions from current dipole sources distributed on a standard cortical space reconstructed from Montreal Neurological Institute (MNI) MRI data.Computer simulations are presented for three different four-shell head models, two with realistic geometry, either surface-based (BEM) or volume-based (FDM), and the corresponding sensor-fitted spherical-shaped model.Realistic geometry turns out to be a relevant factor of improvement, particularly important when considering sources placed in the temporal or in the occipital cortex.

View Article: PubMed Central - PubMed

Affiliation: DEEI, University of Trieste, Via A. Valerio 10, 34127 Trieste, Italy. federica.vatta@deei.units.it

ABSTRACT
The accuracy of forward models for electroencephalography (EEG) partly depends on head tissues geometry and strongly affects the reliability of the source reconstruction process, but it is not yet clear which brain regions are more sensitive to the choice of different model geometry. In this paper we compare different spherical and realistic head modeling techniques in estimating EEG forward solutions from current dipole sources distributed on a standard cortical space reconstructed from Montreal Neurological Institute (MNI) MRI data. Computer simulations are presented for three different four-shell head models, two with realistic geometry, either surface-based (BEM) or volume-based (FDM), and the corresponding sensor-fitted spherical-shaped model. Point Spread Function (PSF) and Lead Field (LF) cross-correlation analyses were performed for 26 symmetric dipole sources to quantitatively assess models' accuracy in EEG source reconstruction. Realistic geometry turns out to be a relevant factor of improvement, particularly important when considering sources placed in the temporal or in the occipital cortex.

Show MeSH