[Eeglablist] Problem with base line in time-frequency

[Arnaud Delorme]

> 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