What happens in mne.viz.Brain when plotting fsaverage?

[Long]

Hi,

I have a question about this function mne.vis.Brain() working with fsaverage.
fsaverage is in the MRI space, so under which coordinate does mne.vis.brain() do the plotting? I think should be the ‘head’ space. If so, then I assume Brain(), in code below, will automatically convert the fsaverage (MRI space) into the ‘head’ space.

brain = mne.viz.Brain(
“fsaverage”,
subjects_dir=subjects_dir,
cortex=“low_contrast”,
alpha=0.25,
background=“white”,
)

Correct me if I am wrong.

Thanks.

[dasdiptyajit (Diptyajit Das)]

Hi long,

Have a look at this:

Source alignment and coordinate frames — MNE 1.9.0 documentation

To your question:
When you call mne.viz.Brain(...), it loads the surface geometry from FreeSurfer and plots it in its native coordinate frame: surface RAS / MRI space

best,
Dip

[Long]

Thank you Dip for answering my question. But I have a followup question. In 5th code block of this working-with-seeg tutorial: Working with sEEG data — MNE 1.9.0 documentation, the plot has two part, first is the plotting of fsaverage, in MRI space as you said:

brain = mne.viz.Brain( “fsaverage”, subjects_dir=subjects_dir, cortex=“low_contrast”, alpha=0.25, background=“white”, )

The next part is the SEEG contacts:
brain.add_sensors(epochs.info, trans=trans)
In above plotting of SEEG electrodes, the trans is calculated as below, which is a transformation to the ‘head’ space:
trans = mne.channels.compute_native_head_t(montage)
So, the contacts are actually plotted in the ‘head’ space.

I don’t understand why these two parts are plotted in different space?