# [Eeglablist] Freq power baseline question

David Ryan ryand1 at goldmail.etsu.edu
Sun Oct 13 15:47:02 PDT 2019

```Hello,

I am looking into frequency power changes with the onset of an
auditory stimulus and a time window of 0-700ms utilizing the script
below. Does this process baseline correct? Does it need a baseline
correction?

I found on the EEGLAB listserv this response; however, I am not
certain my script below provides info on where to take the baseline
from:

> 2- Does "spectopo" function apply baseline normalization by default from EEGLAB GUI?

Yes. To turn it off, you need to use an optional input.

Thanks,
Dave

[spectra,freqs] = spectopo (EEG.data(Fz,:,:), 0, EEG.srate);

%Data ranges
hz8 = find(freqs>7 & freqs<9);
hz7 = find(freqs>6 & freqs<8);
hz6 = find(freqs>5 & freqs<7);
hz5 = find(freqs>4 & freqs<6);
hz4 = find(freqs>3 & freqs<5);

% Compute Power
hz8powerFz = 10^(mean(spectra(hz8))/10);
hz7powerFz = 10^(mean(spectra(hz7))/10);
hz6powerFz = 10^(mean(spectra(hz6))/10);
hz5powerFz = 10^(mean(spectra(hz5))/10);
hz4powerFz = 10^(mean(spectra(hz4))/10);
```