Hello Forum
I have a question about GFP, If I remove some bad epochs manually from the epochs object and I check the GFP of the new evoked object, should I see larger or lower GFP wrt the initial one? Is there any metric (beside visual check) to show if the quality of the evoked response is enhanced or not?
Best,
Payam
it depends. If the bad epochs were very noisy, global field power will go down. If the bad epochs had dead (flat) channels, the GFP will go up after you drop them. Depending on the total number of epochs and the number of bad epochs, the effect may or may not be noticeable on a plot.
In terms of assessing the “quality” of an evoked response, computing signal-to-noise ratio of the expected response (auditory N100, P600, etc) in pre-determined window, relative to the baseline period, is one way to quantify “quality”.