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Canonical source reconstruction for MEG.

Mattout J, Henson RN, Friston KJ - Comput Intell Neurosci (2007)

Bottom Line: Electromagnetic lead fields are computed using the warped mesh, in conjunction with a spherical head model (which does not rely on individual anatomy).This enables the pooling of data from multiple subjects and the reporting of results in stereotactic coordinates.Furthermore, it allows the graceful fusion of fMRI and MEG data within the same anatomical framework.

View Article: PubMed Central - PubMed

Affiliation: INSERM U821, Dynamique Cérébrale et Cognition, Lyon, France. jeremiemattout@yahoo.fr

ABSTRACT
We describe a simple and efficient solution to the problem of reconstructing electromagnetic sources into a canonical or standard anatomical space. Its simplicity rests upon incorporating subject-specific anatomy into the forward model in a way that eschews the need for cortical surface extraction. The forward model starts with a canonical cortical mesh, defined in a standard stereotactic space. The mesh is warped, in a nonlinear fashion, to match the subject's anatomy. This warping is the inverse of the transformation derived from spatial normalization of the subject's structural MRI image, using fully automated procedures that have been established for other imaging modalities. Electromagnetic lead fields are computed using the warped mesh, in conjunction with a spherical head model (which does not rely on individual anatomy). The ensuing forward model is inverted using an empirical Bayesian scheme that we have described previously in several publications. Critically, because anatomical information enters the forward model, there is no need to spatially normalize the reconstructed source activity. In other words, each source, comprising the mesh, has a predetermined and unique anatomical attribution within standard stereotactic space. This enables the pooling of data from multiple subjects and the reporting of results in stereotactic coordinates. Furthermore, it allows the graceful fusion of fMRI and MEG data within the same anatomical framework.

No MeSH data available.


Related in: MedlinePlus

Caudal (upperrow) and ventral (lower row) views of the cortical source energy estimated atthe peak of the M170 for each of the three anatomical models: SCS (a), CCS (b),and TCS (c). Maps have been normalized to their maximum.
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Related In: Results  -  Collection


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fig6: Caudal (upperrow) and ventral (lower row) views of the cortical source energy estimated atthe peak of the M170 for each of the three anatomical models: SCS (a), CCS (b),and TCS (c). Maps have been normalized to their maximum.

Mentions: The two types of event-related fields (faces andscrambled) were subtracted to isolate a face-specific effect occurring around170 milliseconds after stimulation (“M170”). Figure 5 shows the MEG setup andthe M170 component elicited. Average responses, over a time window from 150 to190 milliseconds, were estimated using the three models described above. Theresulting log evidences are shown in Table 1. Figure 6 shows the correspondingmaps of peak responses (conditional expectations of source activity at the timebin containing the maximum response).


Canonical source reconstruction for MEG.

Mattout J, Henson RN, Friston KJ - Comput Intell Neurosci (2007)

Caudal (upperrow) and ventral (lower row) views of the cortical source energy estimated atthe peak of the M170 for each of the three anatomical models: SCS (a), CCS (b),and TCS (c). Maps have been normalized to their maximum.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2266807&req=5

fig6: Caudal (upperrow) and ventral (lower row) views of the cortical source energy estimated atthe peak of the M170 for each of the three anatomical models: SCS (a), CCS (b),and TCS (c). Maps have been normalized to their maximum.
Mentions: The two types of event-related fields (faces andscrambled) were subtracted to isolate a face-specific effect occurring around170 milliseconds after stimulation (“M170”). Figure 5 shows the MEG setup andthe M170 component elicited. Average responses, over a time window from 150 to190 milliseconds, were estimated using the three models described above. Theresulting log evidences are shown in Table 1. Figure 6 shows the correspondingmaps of peak responses (conditional expectations of source activity at the timebin containing the maximum response).

Bottom Line: Electromagnetic lead fields are computed using the warped mesh, in conjunction with a spherical head model (which does not rely on individual anatomy).This enables the pooling of data from multiple subjects and the reporting of results in stereotactic coordinates.Furthermore, it allows the graceful fusion of fMRI and MEG data within the same anatomical framework.

View Article: PubMed Central - PubMed

Affiliation: INSERM U821, Dynamique Cérébrale et Cognition, Lyon, France. jeremiemattout@yahoo.fr

ABSTRACT
We describe a simple and efficient solution to the problem of reconstructing electromagnetic sources into a canonical or standard anatomical space. Its simplicity rests upon incorporating subject-specific anatomy into the forward model in a way that eschews the need for cortical surface extraction. The forward model starts with a canonical cortical mesh, defined in a standard stereotactic space. The mesh is warped, in a nonlinear fashion, to match the subject's anatomy. This warping is the inverse of the transformation derived from spatial normalization of the subject's structural MRI image, using fully automated procedures that have been established for other imaging modalities. Electromagnetic lead fields are computed using the warped mesh, in conjunction with a spherical head model (which does not rely on individual anatomy). The ensuing forward model is inverted using an empirical Bayesian scheme that we have described previously in several publications. Critically, because anatomical information enters the forward model, there is no need to spatially normalize the reconstructed source activity. In other words, each source, comprising the mesh, has a predetermined and unique anatomical attribution within standard stereotactic space. This enables the pooling of data from multiple subjects and the reporting of results in stereotactic coordinates. Furthermore, it allows the graceful fusion of fMRI and MEG data within the same anatomical framework.

No MeSH data available.


Related in: MedlinePlus