[Eeglablist] Power Spectrum question

[nikos dhmou]

Hi list,
I am working on EEG and emotion and I am doing an analysis of power spectrum in different emotion conditions and comparing each condition with the power spectrum, the problem I am facing is that when I compute the spectrum of epochs for some conditions i get negative values and the spectrum is really low so the mean is a negative value. I am using spectopo function and I was wondering if this is correct to get negative values for power for some conditions.1) What wil be the correct form of a power spectrum of an EEG signal to do statistics on it. Would it be the output of spectopo ? or you must normalize this values that you get from spectopo?2) is there another way to use pwech and how to do you calculate alpha using pwelch. Do you need after to normalize the values in order to do your statistics for different conditions (e.g ANOVA).3) What must be the range of values in a power spectrum for the conditions when you use ANOVA.
Thanks 		 	   		  
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