[Eeglablist] Alpha power spectrum assymetry

[Achim, André]

The code below "spectra(1, find(freqs >= 8 | freqs <=13))" uses | (or) instead of & (and), which would return all available frequencies. Besides, the "find" is not necessary; it would be more efficient to write: "spectra(1, freqs >= 8 & freqs <=13)"

André Achim

-----Message d'origine-----
De : eeglablist-bounces at sccn.ucsd.edu [mailto:eeglablist-bounces at sccn.ucsd.edu] De la part de Simon-Shlomo Poil
Envoyé : 19 juin 2011 16:12
À : nikos dhmou; eeglablist at sccn.ucsd.edu
Objet : Re: [Eeglablist] Alpha power spectrum assymetry

Hi Nikos,

The output of spectopo is
 Outputs:
%        spectra  = (nchans,nfreqs) power spectra (mean power over
epochs), in dB
%        freqs    = frequencies of spectra (Hz)

i.e.

[spectra, freqs] = spectopo(..

will give you the spectra with the corresponding frequencies

spectra(1, find(freqs >= 8 | freqs <=13))  should then give you the
alpha frequency band spectrum.

hope it works
-Simon

-- 
Simon-Shlomo Poil

Neuronal Oscillations and Cognition Group (NOC)
Department of Integrative Neurophysiology (INF)
Center for Neurogenomics and Cognitive Research (CNCR)
Neuroscience Campus Amsterdam
VU University Amsterdam
De Boelelaan 1085, Room B-435
1081 HV Amsterdam, The Netherlands

E-mail: simonshlomo.poil at cncr.vu.nl
Phone: +31 20 5989408
Webpage: http://www.poil.dk/s and http://www.cncr.nl



2011/6/19 nikos dhmou <dhmoubagg at hotmail.com>:
> Hello, thank you for your answer my problem is how can i extract the alpha
> band power spectrum only from spectopo. I get a vector of spec of 513 values
> when I use spectopo for a set of epochs in a condition which represent
> frequencies up to 250 hz.
> I only need to calculate this spec value for alpha band to get a mean of
> power spectrum in two certain channels only for alpha band. Sorry but Im
> novice in eeg programming power spectrum
>
> Thanks,
> nikos
>> From: simonshlomo.poil at cncr.vu.nl
>> Date: Sun, 19 Jun 2011 02:47:19 +0200
>> Subject: Re: [Eeglablist] Alpha power spectrum assymetry
>> To: dhmoubagg at hotmail.com
>>
>> Dear Nikos,
>>
>> You can, e.g., use either the 'spec' or 'pwelch' function. They will
>> both give you a full power-spectrum, which you then need to integrate
>> in the alpha frequency band.
>>
>> good luck
>> -Simon
>> --
>> Simon-Shlomo Poil
>>
>> Neuronal Oscillations and Cognition Group (NOC)
>> Department of Integrative Neurophysiology (INF)
>> Center for Neurogenomics and Cognitive Research (CNCR)
>> Neuroscience Campus Amsterdam
>> VU University Amsterdam
>> De Boelelaan 1085, Room B-435
>> 1081 HV Amsterdam, The Netherlands
>>
>> E-mail: simonshlomo.poil at cncr.vu.nl
>> Phone: +31 20 5989408
>> Webpage: http://www.poil.dk/s and http://www.cncr.nl
>>
>>
>> 2011/6/17 nikos dhmou <dhmoubagg at hotmail.com>:
>> > Hello, Im looking a way to calculate power spectrum for alpha band on a
>> > set
>> > of subjects on a set of epochs for two channels and compare anyone has
>> > any
>> > idea ? I use spectopo but it calculates spectrum untill 250 hz not alpha
>> > band. Another problem i have is that the spectrums if i calculate right
>> > give
>> > pretty much the same spectrum for different conditions but that doesnt
>> > make
>> > sense because i want to compare the spectrums for different conditions
>> >
>> > thanks for the help
>> > nikos
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