Q: Issue with source reconstruction on my BEM but not sample's

I am struggling to reconstruct the source of a presumably simple dataset.

The evoked topo (here at 180ms) looks dipolar, and should come from the back of the brain (response to visual stim).

When I reconstruct the source on with the sample BEM, i get something relatively expected (to the extent that it’s in the back of the brain.

However, when I try to reconstruct on my subject’s actual bem, I get very unlikely reconstructions: Here MNE at 180ms reconstruct a frontal activity (similar with dSPM and sLORETA, in mne-python or mne-c):

I checked that the source space and trans alignment make sense (here dipole fit at 180 ms):

I’m using the same evoked and covariance in both cases.

I encounter this issue with all of my subjects.

Any idea in what direction I search?

[I can share the data in private, I haven’t defaced the MRI]

EDIT: this was actually incorrect, I wasn’t using the same covariance across cases.

[larsoner]

I mean that I’m not sure how good the data will be if you just use maxwell_filter to do only a head position change. You can certainly try it. Use the same internal order, external order, and probably no regularization (or maybe the same regularization, which would have been “in” if it had been turned on) and you can probably do it with maxwell_filter. You might end up in some trouble because our calculations are not 100% identical with those of MaxFilter, but you could try it. So it might actually be better if you call MaxFilter with -force to do it for you.

[kingjr]

@dgwakeman ok this seems indeed suboptimal. If I have time I’ll try to get the raw and realign from the beginning.