Hi all, I am trying to fit dipoles on my data using fit_dipole.
I am using “fsaverage”, and currently I am even using template EEG sensor positions (rather than digitized positions), for testing.
To make the situation worse, my template EEG sensor positions were (probably) calculated on a sphere. So, the coregistration of my EEG sensors and “fsaverage” is very bad, see:
The left image shows the situation with trans="fsaverage"
, here NAS, LPA, and RPA are well aligned, but the sensors are partially quite far away from the scalp surface.
The right image shows the situation with a trans
that I computed automatically following Using an automated approach to coregistration — MNE 1.9.0 documentation, so trying to minimize the distance of the sensors from the scalp surface. The result is slightly better (however, NAS, LPA, and RPA are no longer aligned) … but several sensors are still off, and partially too deep inside of the skull.
My question pertains to the sensor positions that are actually used in fit_dipole
. Are the “scalp-projected” sensor positions used (the dark red discs in the images), or are the actual sensor positions used (the light red balls in the images)?
The mne.viz.plot_alignment docstring hints at the “scalp-projected” sensors, see:
And this would also make sense to me, because otherwise, if a sensor is outside of the head, floating in the air, then what “conductivity” could possibly be used.
Does somebody know the answer?
If the “scalp-projected” sensor positions would be used, this would actually allow me to proceed testing with this. I would then likely proceed with the trans
that minimizes the distance of sensors to the scalp (the right side image), even if NAS, LPA, RPA are misaligned.
Eventually, I will have digitized sensor positions, rather than the template EEG sensor positions that I am conducting tests with here.