Thank you so much, Francois!
I did source-level time-frequency transformation in each subject as you advice, and got 'Avg,Power,FreqBands' under each subject. Then I put all the 'Avg,Power,FreqBands' files in Process1, and tried to average (Group files: everything). However, 1 warning occurred as follows. Could you please kind tell me how to correctly do the average? Many thanks!
