[Eeglablist] Epoch length with Spectopo

Krogmeier, Claudia M ckrogmei at purdue.edu
Fri Mar 26 07:15:33 PDT 2021


Hello,

Would someone be able to comment on this script for computing frontal alpha asymmetry after using spectopo to get the power?

 %F3 and F4
  [spectraR,freqsR] = spectopo(EEG.data(12,:,:), 0, EEG.srate);
  [spectraL,freqsL] = spectopo(EEG.data(3,:,:), 0, EEG.srate);

 alphaIdxR = find(freqsR>8 & freqsR<13);
 alphaIdxL = find(freqsL>8 & freqsL<13);

 % Compute absolute power.
 alphaPowerR = mean(10.^(spectraR(alphaIdxR)/10));
 alphaPowerL = mean(10.^(spectraL(alphaIdxL)/10));


 myFAA = (log(alphaPowerR)-log(alphaPowerL));


In the matlab command line, I see " Computing spectra (window length 256; fft length: 256; overlap 0):"

My srate is 256, but my epochs are 6 seconds.  Is the spectra calculated only using one second of my epochs?

Thank you very much for any help,
Claudia




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