[Eeglablist] Differences in Power Spectral density between PRE and POST measurements

[Tyler Durdern]

Dear Cedric,

thank you very much. The LIMO Plugin is quite helpful! I have a quick follow-up question concerning the pre-computation of spectral parameters. I try to compute PSD using the pop_precomp GUI. Whenever I compute power spectrum using ‚specmode' ‚fft‘ everything works fine, but when I switch it to ’specmode' ‚psd‘ I get the following error message:

	Index in position 1 exceeds array bounds. Index must
	not exceed 1.

	Error in spectopo>spectcomp (line 960)
                           	 [tmpspec,freqs] =  pwelch(tmpdata(e,g.boundaries(n)+1:g.boundaries(n+1)),...

	Error in spectopo (line 347)
        	[eegspecdB freqs specstd] = spectcomp( data, frames, srate, epoch_subset, g);

	Error in std_spec (line 328)
        	[X, f] = spectopo(X, size(X,2), EEG(1).srate, 'plot', 'off', 'boundaries', boundaries, 'nfft', g.nfft, 'verbose', 'off', spec_opt{:});

	Error in pop_precomp (line 369)
                [ X f ] = std_spec(TMPEEG, 'channels', { TMPEEG.chanlocs(1).labels }, 'trialindices', { [1:min(20,TMPEEG.trials)] }, 									 'recompute', 'on', 'savefile', 'off', 'trialinfo', struct('condition', ''), spec_params{:});
 
	Error while evaluating UIControl Callback.

I have the Signal Processing Toolbox installed and the only inconsistency in my data is that the number of channels varies between participants as I removed different channels for each participant during preprocessing. I tried different datasets but I still get this error whenever I change specmode to ‚psd‘. Do you have any idea why this happens?

Thanks in advance for your help,

Best,

Tyler


> Am 25.01.2023 um 19:27 schrieb Cedric Cannard <ccannard at protonmail.com>:
> 
> Dear Tyler,
> 
> You can do this type of analysis with EEGLAB STUDY or the LIMO-EEG plugin (linear modeling and more advanced statistics). See here for tuto and examples: https://urldefense.com/v3/__https://eeglab.org/tutorials/10_Group_analysis/study_statistics.html*statistics-on-spectra-itc-and-ersp__;Iw!!Mih3wA!G22IUH-VAEDVJGJAXQGf3kh5kxhuuyFKs3hQ1Laj7rp5_r4ZNZMPX3w4hIYlJVfT-LTrRUAG8M_2ayv3KSY$ 
> 
> 
> Cedric
> 
> 
> 
> ------- Original Message -------
> On Tuesday, January 24th, 2023 at 6:10 AM, Tyler Durdern <ty_du at gmx.de> wrote:
> 
> 
>> Dear all,
>> 
>> I am currently analyzing resting state EEG data with EEGlab. I intend to compare power spectral densities (PSD) between PRE and POST measurements. Is there a way to statistically compare PSD in such a way and importantly to plot the significant differences in PSD between PRE and POST on a topographical map using EEGlab. Additionally, is it possible to correlate and subsequently plot PSD differences between PRE and POST with behavioral data using EEGlab. I searched the net but I cannot find a sufficient solution.
>> 
>> Your help is much appreciated.
>> 
>> Best,
>> 
>> Ty
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