Hi MNE users,
I am currently working on combined HD-EEG and MEG file to see the source localization of a stimulation activity performed for my subjects. I am working on both brainstorm and MNE and trying to see how the results differ across the two softwares. One interesting finding that I noticed with Brainstorm is that the first peak of the evoked response in case of EEG is around 10ms faster than that of MEG’s first peak. This has remained the case for almost all the subjects that I am working on, and this can be possibly explained by the different things that EEG and MEG looks at.
When I try doing the same thing with MNE, I have noticed that for the topography at different time points for EEG and MEG sensors, EEG sensors show activity in the specific area of the brain around 10ms earlier than that of MEG sensors which is pretty much the same result I see from inverse model in brainstorm.
However, when plotting the inverse model on MNE, I see that the first peak response is localized in the brain at roughly the same time for HD-EEG and MEG (62 ms after the stimulus given in my case). With brainstorm, I saw the EEG produced first response at 51 ms. But with MNE, at that given time stamp, there is no localization of the activity.
Is it to do something with how the algorithm works differently across both softwares or is it an error in inverse modelling?
The method used in both the cases is dSPM,
For MNE, I used
snr=3
lambda2= 1./snr **2
Will changing the snr and lamba parameters made any difference in the time? What is the ideal snr and lambda value if any?