time-frequency spectrum of event related potentials

Hi,

I am working with auditory evoked potentials (EEG). I have 100 trials. I can make time-frequency spectrum of averaged signal (from 100 trials) with using software e. g. EEGLAB.

But I would like make time-frequency spectrum of each trial and after that create average spectrum. I can create FOR loop, where each step makes time-frequency spec. from one trial. Then I have 100 T-F Spec. But I don't know how to 'piece together' individual trial spectrums to gain averaged spectrum.

Is it at all possible ? Some basic idea ? many thanks

[Daniel kiracofe]

How are you making the individual time-frequency spectrums? spectrogram? If so, you just need a loop like

for i=1:100
  [S(i,:,:),F,T] = spectrogram(...)
end
AvgS = mean(S, 1);

Does this answer the question?

[kubyk]

For individual t-f spec. I used matlab toolbox LTFAT. It has function scgram, similar to spectrogram in Matlab.

I solved my problem yet (not elegant at all) but I will try it with your advice one more time.

Answer 1

[Star Strider]

I would not use the time-frequency spectra for each trial to calculate the average spectrum for the trial. I would simply take the fft of the entire signal for each trial and use that as the average.

[kubyk]

I need know something about changing frequencies in time, therefore I think t-f spectrum is good for that problem.