[Eeglablist] changes in spectopo?

[Arnaud Delorme]

Dear Wambua,

you should most likely use the pwelch method (implemented in the  
EEGLAB spectopo function). It is a windowed FFT (several FFT averaged).
The Thomson method (usually known as multitaper) is good too. It is  
first projecting the data onto an orthogonal base, then performing FFT.

They should all return similar results (FFT, pwelch, multitaper). I  
guess the Thomson method is the less sensitive to noise but also the  
most complex to use. I guess it would also be possible to use the  
welch method on top of multitaper. It is all a matter of preference. I  
would advised using the pwelch method which is easy (you just give as  
an option the length of the windows and the overlap). Multitaper would  
require you to select the number of basis vector in your othogonal  
base and this is much less intuitive (and also has consequences on the  
frequency resolution you can achive).

Hope this helps,

Arno


On Aug 6, 2009, at 12:22 PM, Wambua Kazi wrote:

> Dear esteemed colleagues,
>     I am trying the estimate the mean EEG spectra of epoched data.   
> I addition to an FFT, there are at least two methods implemented in  
> Matlab for this purpose: [1] pwelch.m (Welch's method, EEGLAB uses  
> this) and [2] pmtm.m (Thomson's multitaper method).
>     Can anyone tell me what the relative pro's and con's of the  
> Welch and Thomson method are for about 1-2 second epoched data  
> (around 256-512 time points)?
>             thank you for your time,
>                      -Wambua
>
>
> <ATT00001.txt>