[FieldTrip] why are grid points located outside the brain?

Balderston, Nicholas (NIH/NIMH) [F] nicholas.balderston at nih.gov
Wed Apr 20 23:27:00 CEST 2016


Dear all,

Thanks for the question Maris, I have been wondering the same.

Along those lines, I was wondering if it is appropriate to scale the resulting beamformer grids to match the size of the MNI template after the fact?

thanks,
-nick
________________________________
From: Maris Skujevskis [icelandhouse at gmail.com]
Sent: Wednesday, April 20, 2016 11:11 AM
To: fieldtrip at science.ru.nl
Subject: [FieldTrip] why are grid points located outside the brain?

Dear Fieldtrip users,

Can someone please explain the reason why in the tutorial http://www.fieldtriptoolbox.org/tutorial/sourcemodel<redir.aspx?REF=LS5FarOkwP8TA2JeL7GD9rSHEi2JYy_dxSVgVGLmjLdHy0UjYmnTCAFodHRwOi8vd3d3LmZpZWxkdHJpcHRvb2xib3gub3JnL3R1dG9yaWFsL3NvdXJjZW1vZGVs> (or in general, for that matter) the outer layer of grid points of the source model lie outside the brain though they are defined as being inside?

This is what I am refering to:
http://www.fieldtriptoolbox.org/_detail/example/mnispace/mni_fig1a.png?id=tutorial%3Asourcemodel<redir.aspx?REF=J-IFW_IErPmt-H_p_1iAMMmBolt7L30eL_pBM_V-01ZHy0UjYmnTCAFodHRwOi8vd3d3LmZpZWxkdHJpcHRvb2xib3gub3JnL19kZXRhaWwvZXhhbXBsZS9tbmlzcGFjZS9tbmlfZmlnMWEucG5nP2lkPXR1dG9yaWFsJTNBc291cmNlbW9kZWw.>
http://www.fieldtriptoolbox.org/_detail/example/mnispace/mni_fig2b.png?id=tutorial%3Asourcemodel<redir.aspx?REF=IaWdzywIa_3ynNHRiYt0MV-WBFl023gts5LLPWE1GlZHy0UjYmnTCAFodHRwOi8vd3d3LmZpZWxkdHJpcHRvb2xib3gub3JnL19kZXRhaWwvZXhhbXBsZS9tbmlzcGFjZS9tbmlfZmlnMmIucG5nP2lkPXR1dG9yaWFsJTNBc291cmNlbW9kZWw.>

According to my naive understanding, this means that in this model the potential neural sources may also lie outside the brain, which makes no sense. Clearly, I am missing something here...

Thanks!

Maris

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