almost all of my frequency analysis result is like shown in the screenshot,mostly focus on low frequency under 10hz,does it mean lack of higher frequency signal?or that's only because I didn't do baseline normalization.after i do a baseline normalization,the result seems normal.I want to ask :is baseline normalization a must-thing to do?if we ignore,the results will be like screeshot shown above,aren't they?
These questions are discussed in the tutorial about time-frequency:
http://neuroimage.usc.edu/brainstorm/Tutorials/TimeFrequency#Normalized_time-frequency_maps