Cargando…

Similarities Between Simulated Spatial Spectra of Scalp EEG, MEG and Structural MRI

Electrical dipoles oriented perpendicular to the cortical surface are the primary source of the scalp EEGs and MEGs. Thus, in particular, gyri and sulci structures on the cortical surface have a definite possibility to influence the EEGs and MEGs. This was examined by comparing the spatial power spe...

Descripción completa

Detalles Bibliográficos
Autores principales: Ramon, Ceon, Freeman, Walter J., Holmes, Mark, Ishimaru, A., Haueisen, Jens, Schimpf, Paul H., Rezvanian, Elham
Formato: Texto
Lenguaje:English
Publicado: Springer US 2009
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2749166/
https://www.ncbi.nlm.nih.gov/pubmed/19557510
http://dx.doi.org/10.1007/s10548-009-0104-7
_version_ 1782172165063311360
author Ramon, Ceon
Freeman, Walter J.
Holmes, Mark
Ishimaru, A.
Haueisen, Jens
Schimpf, Paul H.
Rezvanian, Elham
author_facet Ramon, Ceon
Freeman, Walter J.
Holmes, Mark
Ishimaru, A.
Haueisen, Jens
Schimpf, Paul H.
Rezvanian, Elham
author_sort Ramon, Ceon
collection PubMed
description Electrical dipoles oriented perpendicular to the cortical surface are the primary source of the scalp EEGs and MEGs. Thus, in particular, gyri and sulci structures on the cortical surface have a definite possibility to influence the EEGs and MEGs. This was examined by comparing the spatial power spectral density (PSD) of the upper portion of the human cortex in MRI slices to that of simulated scalp EEGs and MEGs. The electrical activity was modeled with 2,650 dipolar sources oriented normal to the local cortical surface. The resulting scalp potentials were calculated with a finite element model of the head constructed from 51 segmented sagittal MR images. The PSD was computed after taking the fast Fourier transform of scalp potentials. The PSD of the cortical contour in each slice was also computed. The PSD was then averaged over all the slices. This was done for sagittal and coronal view both. The PSD of EEG and MEG showed two broad peaks, one from 0.05 to 0.22 cycles/cm (wavelength 20–4.545 cm) and the other from 0.22 to 1.2 cycles/cm (wavelength 4.545–0.834 cm). The PSD of the cortex showed a broad peak from 0.08 to 0.32 cycles/cm (wavelength 12.5–3.125 cm) and other two peaks within the range of 0.32 to 0.9 cycles/cm (wavelength 3.125–1.11 cm). These peaks are definitely due to the gyri structures and associated larger patterns on the cortical surface. Smaller peaks in the range of 1–3 cycles/cm were also observed which are possibly due to sulci structures. These results suggest that the spatial information was present in the EEG and MEG at the spatial frequencies of gyri. This also implies that the practical Nyquist frequency for sampling scalp EEGs should be 3.0 cycles/cm and an optimal interelectrode spacing of about 3 mm is needed for extraction of cortical patterns from scalp EEGs in humans.
format Text
id pubmed-2749166
institution National Center for Biotechnology Information
language English
publishDate 2009
publisher Springer US
record_format MEDLINE/PubMed
spelling pubmed-27491662009-09-23 Similarities Between Simulated Spatial Spectra of Scalp EEG, MEG and Structural MRI Ramon, Ceon Freeman, Walter J. Holmes, Mark Ishimaru, A. Haueisen, Jens Schimpf, Paul H. Rezvanian, Elham Brain Topogr Original Paper Electrical dipoles oriented perpendicular to the cortical surface are the primary source of the scalp EEGs and MEGs. Thus, in particular, gyri and sulci structures on the cortical surface have a definite possibility to influence the EEGs and MEGs. This was examined by comparing the spatial power spectral density (PSD) of the upper portion of the human cortex in MRI slices to that of simulated scalp EEGs and MEGs. The electrical activity was modeled with 2,650 dipolar sources oriented normal to the local cortical surface. The resulting scalp potentials were calculated with a finite element model of the head constructed from 51 segmented sagittal MR images. The PSD was computed after taking the fast Fourier transform of scalp potentials. The PSD of the cortical contour in each slice was also computed. The PSD was then averaged over all the slices. This was done for sagittal and coronal view both. The PSD of EEG and MEG showed two broad peaks, one from 0.05 to 0.22 cycles/cm (wavelength 20–4.545 cm) and the other from 0.22 to 1.2 cycles/cm (wavelength 4.545–0.834 cm). The PSD of the cortex showed a broad peak from 0.08 to 0.32 cycles/cm (wavelength 12.5–3.125 cm) and other two peaks within the range of 0.32 to 0.9 cycles/cm (wavelength 3.125–1.11 cm). These peaks are definitely due to the gyri structures and associated larger patterns on the cortical surface. Smaller peaks in the range of 1–3 cycles/cm were also observed which are possibly due to sulci structures. These results suggest that the spatial information was present in the EEG and MEG at the spatial frequencies of gyri. This also implies that the practical Nyquist frequency for sampling scalp EEGs should be 3.0 cycles/cm and an optimal interelectrode spacing of about 3 mm is needed for extraction of cortical patterns from scalp EEGs in humans. Springer US 2009-06-26 2009-11 /pmc/articles/PMC2749166/ /pubmed/19557510 http://dx.doi.org/10.1007/s10548-009-0104-7 Text en © The Author(s) 2009
spellingShingle Original Paper
Ramon, Ceon
Freeman, Walter J.
Holmes, Mark
Ishimaru, A.
Haueisen, Jens
Schimpf, Paul H.
Rezvanian, Elham
Similarities Between Simulated Spatial Spectra of Scalp EEG, MEG and Structural MRI
title Similarities Between Simulated Spatial Spectra of Scalp EEG, MEG and Structural MRI
title_full Similarities Between Simulated Spatial Spectra of Scalp EEG, MEG and Structural MRI
title_fullStr Similarities Between Simulated Spatial Spectra of Scalp EEG, MEG and Structural MRI
title_full_unstemmed Similarities Between Simulated Spatial Spectra of Scalp EEG, MEG and Structural MRI
title_short Similarities Between Simulated Spatial Spectra of Scalp EEG, MEG and Structural MRI
title_sort similarities between simulated spatial spectra of scalp eeg, meg and structural mri
topic Original Paper
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2749166/
https://www.ncbi.nlm.nih.gov/pubmed/19557510
http://dx.doi.org/10.1007/s10548-009-0104-7
work_keys_str_mv AT ramonceon similaritiesbetweensimulatedspatialspectraofscalpeegmegandstructuralmri
AT freemanwalterj similaritiesbetweensimulatedspatialspectraofscalpeegmegandstructuralmri
AT holmesmark similaritiesbetweensimulatedspatialspectraofscalpeegmegandstructuralmri
AT ishimarua similaritiesbetweensimulatedspatialspectraofscalpeegmegandstructuralmri
AT haueisenjens similaritiesbetweensimulatedspatialspectraofscalpeegmegandstructuralmri
AT schimpfpaulh similaritiesbetweensimulatedspatialspectraofscalpeegmegandstructuralmri
AT rezvanianelham similaritiesbetweensimulatedspatialspectraofscalpeegmegandstructuralmri