Good morning Francois et al.
We have a graduate student who has created source waveforms from data acquired with EEG (min-norm/sLORETA) that resulted in 3 waveforms (uncontrained: x,y,z directions). The "constrained" option was not available (greyed out), however, we would like to use it. Is there some way to make it happen?
Merci!
Fil
Hi Fil:
The constrained option should be available when deriving the head model prior to source modeling, if a cortical surface (from the individual or a template) is made available in the anatomy folder of that participant.
This menu is not available if you are using a volume head model, but only if you used the cortex as the source space.
Have you sorted out your problem?
Thank you Francois. Yes, we realized that we need to use cortical surface as source space. Working on it now! Cheers!
Good morning Francois and Sylvain,
Your recommendation worked regarding cortical surface as source space! Thank you!
However, we found that source waveforms we much smaller in amplitude as compared to other source modelling software (i.e., over 10 uV amplitude vs 0.5 uV at visual cortex locations) as well as much smaller in amplitude in sensor space. We are wondering whether this is a if there is a scaling issue? Any thoughts on this situation? If you need more information, we are happy to provide. Cheers and thank you.
Fil
There are no microVolts here: The minimum norm solution is in pA.m, sLORETA give you a unitless statistic.