Please see attached screenshot. What causes the topo plot to be slanted with respect to the "ears" and "nose"? The registration seems adequate, but I'd like to solve the problem of the auditory evoked response being localized to the occipital lobe.
Could it be one or a few sensors declared as bad over the left frontal region? Can you also post a lateral view of the MEG/3S sensor + head surface please?
This tilt in the topography is due to the position of the head of the subject with respect with the MEG helmet.
In the "2D Sensor cap" view, the vertical axis represents is defined by the X axis of the SCS coordinates, which is given by the position of the Nasion. The 2D representation of the helmet shows the actual position of the helmet in this referential.
https://neuroimage.usc.edu/brainstorm/CoordinateSystems
The bottom figure confirms that the subject head and the helmet are not aligned.
The central vertical series of green dots are probably supposed to be located on the nose crest, but they appear clearly shifted towards the left eye of the participant.
My guess is that there is an issue with the registration of the MEG with the anatomy of the subject, possibly on top of a subject that is already not sitting straight in the MEG.
You can fix the registration manually if none of the default registration options (based on the fiducials or the other digitized head points):
https://neuroimage.usc.edu/brainstorm/Tutorials/ChannelFile#Automatic_registration
https://neuroimage.usc.edu/brainstorm/Tutorials/ChannelFile#Manual_registration
You're right, the nose doesn't look great. I'll take a look at the nasion position and then attempt manual registration. Thanks!