[Eeglablist] Problem with base line in time-frequency

[Johan.poncelet]

Thanks Brian for your proposition but my protocol dont permit me to try 
with a bigger epoch than -1000 to 2000.

Brian Roach a écrit :
> In addition to what has already been covered, you should know that you 
> will need longer epochs to use -1000 to -500ms as your baseline.  
> Depending on what you decide to examine as the lowest frequency, that 
> will determine the necessary epoch length.  From the -126 to 1200ms 
> window you describe, I believe you need to have epochs starting around 
> -2000 or -1900
> At 07:25 AM 8/7/2007, Arnaud Delorme wrote:
>
>> > I have epoched my data from -1000 ms to +2000ms in order to have a 
>> very
>> > large one.
>> > When I apply the time frequency function (study, compute ERSP), I 
>> obtain
>> > a time freq representation from -126ms to 1200ms maxi.
>> >
>> > Why?
>> >
>>
>> This is because the time-frequency decomposition trim the time window.
>> If your lower frequency is 3 Hz and you have a 3-cycle wavelet (at 3
>> Hertz) for instance, this wavelet duration is 1000 ms (1 s). This means
>> that 500 ms will be trimmed on each side.
>>
>> > Now i would like to do different ERSP. I would like that the [-1000,
>> > -500] period to be my baseline. And then have a representation from 
>> -500
>> > to +1500.  Is it possible? I have tried with the option 'baseline' in
>> > the ERSP box but EEGlab give me error message.
>> >
>>
>> The baseline cannot be entered yet through this interface but we have
>> entered an bug repport for enhancement so this should be possible soon.
>>
>> Best regards,
>>
>> Arno
>>
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>


-- 
Johan Poncelet
Laboratoire Neuroscience et Systèmes Sensoriels
CNRS UMR 5020
Equipe Variabilité et Plasticité de l'Audition
Université Claude Bernard Lyon 1
50, avenue Tony Garnier
69366 LYON cedex 07
Tel 06 81 88 66 92
Johan.poncelet at olfac.univ-lyon1.fr
Johan.poncelet at gmail.com