Thanks a lot for your explanation! Now I understand how it’s done. I have a follow-up question and hope to get your insight.
After preprocessing my ER (prepare, maxfilter, then bandpass filter and apply ICA in the same way as my experiment recording), I computed the covariance matrix and found they have a pattern quite different from what I see in the tutorial:
Such a quadratic pattern, instead of a dominating diagonal line, appeared in all four participants’ data that I tested. Does this indicate something was screwed up in the processing, or just reflecting the property of our facility? What would be a good way to diagnose the noise covariance matrix?
Yaqing