Hey,
i want to know what is the difference between “constraint or unconstrained”, Source Model Dipole Orientation For EEG Data.
When I am turning of absolute values in unconstrained it is only giving me positive values in colorbar (figure), but when I am turning off absolute values in constrained it is giving me negative as well positive values in colorbar (figure). why is that?
does unconstrained work on GFP? or what is the reason for showing positive values in this case and not in other case?
I want to know which Source Model Dipole Orientation is correct/accurate For EEG Data, “constraint or unconstrained”? on website it is mentioned to use unconstrained, what is significance of using only unconstrained?
Dear Hasan,
The positive/negative values are well explained in the Source estimation tutorial:
http://neuroimage.usc.edu/brainstorm/Tutorials/SourceEstimation#Sign_of_constrained_maps
People in EEG source modeling tend to use unconstrained models, as illustrated in the EEG/Epilespy tutorial, because it produces smoother maps. EEG does not have the spatial resolution we can expect from MEG, the information we collect at the surface of the head is a lot more smeared, so there is no hope to localize precisely the activity within a sulcus.
http://neuroimage.usc.edu/brainstorm/Tutorials/Epilepsy
Please read carefully all the introduction tutorials and get back to us if you have more questions.
Thanks,
Francois
(see your other post: http://neuroimage.usc.edu/forums/showthread.php?2687-Export-channels-from-EEG-Data)
