using coil/isotrack information for sourceanalysis (neuromag data)

[Hanneke Van Dijk]

Dear all,

In my group we have a question regarding the use of the coil locations and/ or isotrack data to do source analysis. We are doing data analysis using FT and the MNE toolbox, on a dataset recorded with a Neuromag122 system. 

The four coils were placed in different locations then in the CTF system, which uses the anatomical landmarks (left ear, right ear and nasion). Here we placed the coils on the scalp; two approximately above the eyes and two behind the ears. We digitized the locations of the coils using the polhemus, togheter with the anatomical landmarks and some more points. We would very much like to know HOW and WHERE fieldtrip uses the coil-location information and if it is possible to use the polhemus data as well, to place the head at the correct location within the helmet and to do sourceanalysis.

I noticed allready that when reading the fiff file with 'fiff_read_meas_info' (MNE) there is a field called .dig which seems to contain the coordinates of digitized locations. I have no idea though how to integrate this information into the data so fieldtrip can use it.

Thanks in advance for any information,

Hanneke van Dijk

Institute for Clinical Neuroscience and Medical Psychology,
Heinrich Heine Universitaet, Duesseldorf.



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