# question on mne\_surf2bem for MEG/EEG combined

**URL:** <https://mne.discourse.group/t/question-on-mne-surf2bem-for-meg-eeg-combined/98>\
**Category:** Mailing List Archive (read-only)\
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**Created:** [February 25, 2009, 2:34pm UTC](https://mne.discourse.group/t/question-on-mne-surf2bem-for-meg-eeg-combined/98 "2009-02-25T14:34:46Z")\
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**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\
**Post date:** [February 25, 2009, 2:34pm UTC](https://mne.discourse.group/t/question-on-mne-surf2bem-for-meg-eeg-combined/98/1 "2009-02-25T14:34:46Z")

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Dear all,

I am a new user of MNE (post-doc MRC-CBU, Cambridge, UK),  
and I already have some question for this mailing list.

I am analysing data that combined MEG & MEG and I have a question on the  
following command (taken from MEG analysis alone)

mne\_surf2bem --surf $SUBJECTS\_DIR/\<participant\>/surf/lh.smseghead --id 4 --fif \<participant\>-head.fif

For the EEG I need 3 layers BEM (skull, brain and skin)

In the manual for MNE p76 it says " --surf \<name\>" Specifies a  
FreeSurfer binary format surface file. Before specifying  
the next surface (--surf or --tri options) details of the surface  
specification can be given with the options listed in Section 5.4.2. "  
for the --id option, the identification number to assign to this  
surface. (1 = inner skull, 2 =outer skull, 4 = scalp).

My question is the following  
On this command above the file lh.smseghead correspond to the layer bem  
of the scalp (--id 4) ONLY or is there also inside the info for the  
other layers ???  
If the info for the other layers are also in the same file how I do I  
write the proper command

mne\_surf2bem --surf $SUBJECTS\_DIR/\<participant\>/surf/lh.smseghead --id 4  
--id 2 --id 1 --fif \<participant\>-head.fif

or do I need to call 3 times the same file?

mne\_surf2bem --surf $SUBJECTS\_DIR/\<participant\>/surf/lh.smseghead --id 4  
--surf $SUBJECTS\_DIR/\<participant\>/surf/lh.smseghead --id 2  
--surf $SUBJECTS\_DIR/\<participant\>/surf/lh.smseghead --id 1  
--fif \<participant\>-head.fif

If this is not the case that the different layers are in the same file,  
which files should I prompt? in the directory /surf/ they are 56 others  
and it is not explained anywhere which is what. (btw, I do not  
understand why this file has "lh." affix does that mean it is only for  
left hemisphere? there are also "rh." files...)

Thanks in advance for your help

Regards,

E. Fonteneau