Baseline Standardization of Spectral Granger Causality Maps from ictal onset

I am performing Spectral Granger Causality analysis on seizure onsets from MEG data. I am trying to standardize individual maps in relation to a baseline free of discharges from the same subject. My epochs are too short (4s each). I extracted the frequency of interest for each epoch and in process 2, I ran STANDARDIZE> BASELINE NORMALIZATION (A = baseline) and selected Z-score transformation. When I do that, I receive a warning “you cannot use this process to normalize PSD files because they do not have a time dimension”. Can I ignore the warning and use the final map? Do you have any suggestions on how to perform the baseline standardization? Thanks.

Are you trying to normalize the connectivity files (Granger causality results)?
This is indeed not possible, there is no baseline in your data because there is no time at all.
The Granger causality files have only one value per pair of signals and per frequency. You can't compute a mean or std over a baseline.

If you want to compare the connectivity values obtained between a resting state and an active state, you can compute the GC for the resting condition, the GC for the active condition, and then run a non-parametric t-test across subjects.