[FieldTrip] Time-frequency analysis without baseline

[Jochem Rieger]

Hi Bence,

the baseline should go into FFT's 0 Hz frequency coefficient, which is 
the mean of the analysis window

Best,

     Jochem


On 21.07.23 10:52, Bence Szaszkó via fieldtrip wrote:
>
> ACHTUNG!Diese E-Mail kommt von Extern! WARNING! This email originated 
> off-campus.
>
> Hello fellow FieldTrippers,
>
> I am analyzing steady-state data where I first had to select the first 
> 10s after a certain event and then, within these 10s chunks, create 
> regular epochs of 2s length using the pop_regepoch function of EEGlab. 
> I did the spectral analysis with Fieldtrip and it went just fine; but 
> now, I have to perform time-frequency analysis of the first 2s of 
> those 10s chunks (so the first epoch in every chunk); however, due  to 
> the limitations of pop_regepoch, I do not have a baseline, but only 
> the 2s, with time 0 being the time-locking stimulus.
>
> So now, I cannot perform baseline correction on the data, as I do not 
> have a baseline. Do you have any idea how to circumvent this? Keep in 
> mind that the epoch before the epoch in question is not the preceding 
> epoch in time, so we cannot use that unfortunately. Or is it okay to 
> not correct the baseline at all?
>
> In the spectral analysis, I used a signal-to-noise ratio instead of 
> raw or log power, where I divided the raw power of Frequency N through 
> the sum of the raw powers of N-1, N-2, N+1 and N+2. Would this also 
> work for the time-frequency domain, doing this for each timepoint and 
> channel?
>
> Kind regards,
> Bence
> -- 
> Bence Szaszkó, BSc MA MSc
> University Assistant (prae doc)
>
> Vienna Doctoral School CoBeNe
> PhD Representative
>
> University of Vienna
> Faculty of Psychology
> Department of Cognition, Emotion, and Methods in Psychology
>
> Liebiggasse 5
> A-1010 Wien/Vienna
> Austria
>
> e-mail: bence.szaszko at univie.ac.at
>
>
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-- 
Jochem Rieger
Prof. Dr. rer. nat. habil.
Applied Neurocognitive Psychology
DFG Center for Open and Reproducible Neuroscience Tools
NFDI sections ELSA and metadata

Carl-von-Ossietzky University Oldenburg
Phone: +49 (0)441 798 4533
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