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mne-tools / mne-python

MNE: Magnetoencephalography (MEG) and Electroencephalography (EEG) in Python
https://mne.tools
BSD 3-Clause "New" or "Revised" License
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DOC: Clarify 1-layer BEM+EEG error message #6315

Closed jgeller112 closed 5 years ago

jgeller112 commented 5 years ago

Hello,

I am having issues calculating the forward solution. I get the error: “Cannot use a homogeneous model in EEG calculations.” What are some reasons for this error?

jgeller112 commented 5 years ago

Related to this issue, has there been a solution to the following error:

Surface inner skull is not completely inside surface outer skull

larsoner commented 5 years ago

I get the error: “Cannot use a homogeneous model in EEG calculations.” What are some reasons for this error?

This means you tried to use a 1-layer BEM instead of a 3-layer BEM when doing forward calculations with EEG channels.

Surface inner skull is not completely inside surface outer skull

This means that your inner_skull.surf overlaps with outer_skull.surf. Usually this happens when using the watershed bem, and Freesurfer did a bad job of approximating the inner skull surface (which is created just by expanding the brain.surf) and/or the outer_skull.surf (which is created by shrinking the outer_skin.surf. You can visualize this stuff with freeview.

For further questions about how to get usable surfaces, the mne_analysis listserv is probably a better place so that more people with analysis knowledge and experiences can chime in and learn. GitHub issues are mostly for reporting bugs and/or enhancement requests. I'll leave this open and re-title so we remember to clarify the error message about 1- vs 3-layer BEM.