[Eeglablist] When to apply pop_rmbase
#HENG JIAMIN GLADYS#
JHENG007 at e.ntu.edu.sg
Thu Jul 29 01:02:08 PDT 2021
Dear EEGLAB list,
I have a query as to when to apply baseline correction via the function "pop_rmbase".
I am working on a dataset that is looking at extracting the power spectra in alpha/theta/beta frequency bands during music listening. Participants listened to several musical excerpts (each 45 sec) with a 15 sec break in between music stimuli.
In my preprocessing pipeline, I included a step that did a baseline correction of -1 second to each epoch (i.e. individual music clips) because "Removing a mean baseline value from each epoch is useful when baseline differences between data epochs (e.g., those arising from low-frequency drifts or artifacts) are present." (https://urldefense.proofpoint.com/v2/url?u=https-3A__eeglab.org_tutorials_07-5FExtract-5Fepochs_Extracting-5FData-5FEpochs.html-23removing-2Dbaseline-2Dvalues&d=DwIF-g&c=-35OiAkTchMrZOngvJPOeA&r=kB5f6DjXkuOQpM1bq5OFA9kKiQyNm1p6x6e36h3EglE&m=auzm18_BF9WNzeSRvFPDKEM_SiUEsNWpxiyza9uzEXs&s=M3eOWlwNSQ45fvEuz0e7s1Iz5guLQT6oflUFx_DL_4Q&e= )
As such, following is my pipeline:
1. Bandpass filter 1 – 30 Hz
2. Remove noisy channels (threshold: above kurtosis 5)
3. Average re-reference
4. Epoch: baseline correction of -1 second (i.e. -1 sec to 45 sec)
6. Re-epoch from 0 sec to 45 sec
7. Apply ICA
8. Remove ICs related to eye-blinks and muscle artefacts using MARA
9. Remove EOG channels
11. Extract power spectra values for each epoch
Is it appropriate to apply the baseline correction of -1 second before epoch (i.e. Step 4)? Or should the baseline correction be done after calculating spectral power values, and not at the raw EEG values (i.e. Step 11)?
I would greatly appreciate any reference to a paper that shows the theoretical basis of why doing baseline correction before epoch is okay.
Thank you very much in advance!
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