[FieldTrip] BTI freesurfer surface

Schoffelen, J.M. (Jan Mathijs) jan.schoffelen at donders.ru.nl
Wed Mar 8 17:55:22 CET 2017

Hi Nick,

Sounds like you need a transformation matrix from freesurfer space to  MEG headspace, true?

is there a c_ras.mat file in your freesurfer/mri directory? This may provide you with the missing link


J.M.Schoffelen, MD PhD
Senior Researcher, VIDI-fellow - PI, language in interaction
Telephone: +31-24-3614793
Physical location: room 00.028
Donders Centre for Cognitive Neuroimaging, Nijmegen, The Netherlands

On 08 Mar 2017, at 17:48, Nicholas A. Peatfield <nick.peatfield at gmail.com<mailto:nick.peatfield at gmail.com>> wrote:

Hi Fieldtrippers

I want to reconstruct cortical sources using a freesurfer surface, rather than an equidistant grid I will use the points from the surface. To do so I use ft_read_headshape to read the .surf file and use it as the points for the leadfield. However, the MEG data and headmodel are in 'bti' coordinates thus the grid points are not aligned to the headmodel and sensor points.

I read the minimum norm estimate tutorial from fieldtrip webpage for transforming spm coordinates to bti, but in my case I am using a surface file in which there are only the points and tri.gonometries and the tutorial doesn't apply.

How can I convert the surface points to bti? This is HCP data and I thought I would find some help on this somewhere but couldn't.



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