[Mne_analysis] Error running make_forward_solution: Head<-->sensor transform not found

[Hari Bharadwaj]

Hi Emily,
   Perhaps you could try converting the digitization data to one of the
formats (e.g., .hpts) accepted by mne.channels.read_montage(.) using
the C-version of mne_convert_dig_data (if they are already not
available in one of those formats). Once you do that and read it into
python as a Montage object using mne.channels.read_montage(.), you
could supply it as to the montage argument in 
mne.io.read_raw_brainvision(.).

Also, the digitization data should contain cardinal points (like nasion,
LPA, RAP) for the head along with the EEG sensor locations.. That way,
"head coordinated" and "sensor coordinates" can be matched in the Montage.

HTH,
Hari


On Tue, November 17, 2015 7:07 pm, Emily Stephen wrote:
> Hi All,
>
> I'm getting an error when I run mne.make_forward_solution, but only if I
> try to save the result.
>
> That is, if I set fname=None then the whole thing runs fine, but if I set
> fname=<filename>, it fails in the call to write_forward_solution with the
> error:
> Head<-->sensor transform not found
>
> Seems like write_forward_solution is expecting values in info under
> dev_head_t or ctf_head_t, which never got set.
>
> I think it may be related to the fact that I'm loading (just EEG) data
> from
> a brainvision file using mne.io.read_raw_brainvision.
>
> I've been struggling to figure out how to include the digitizer
> information
> in the preprocessed data. My digitizer info is in a .fif file that
> otherwise doesn't contain any measurement data (I can't even figure out
> how
> to load it using the python MNE). So far the only thing I've done with
> that
> file is to use it to update the channel locations with a call to the C
> implementation:
>     call(['mne_check_eeg_locations',
>           '--file', fname,
>           '--dig', op.join(subjects_dir,subject,subject + '.fif'),
>           '--fix'])
>
> I'm new to all of this (including python) so any help would be much
> appreciated! I've attached the code (apologies for the mess).
>
> Thanks,
> Emily
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-- 
Hari Bharadwaj
Research Fellow
Martinos Center for Biomedical Imaging,
Massachusetts General Hospital
149 Thirteenth Street,
Charlestown, MA 02129

hari at nmr.mgh.harvard.edu
Ph: 734-883-5954
www.haribharadwaj.com