[FieldTrip] relative power estimation

[Marta Andujar]

Hi  Stephen,
thank you for the quick reply, having a data structure which is baseline
corrected is exactly what I want.
The other question concerns the frequency-band specific
baseline-correction. As a first step I computed TFR representation of the
entire frequency spectrum (i.e. from 8 HZ to 180 HZ), since I am interested
in inspecting the data in this spectrum (In this case applying the
baseline-correction just before plotting is ok). From this data structure
I subsequently extract different frequency-bands by cutting the data
(TFRwavedata) at different frequencies (e.g 12 Hz, 30 Hz and so on) in
order to obtain four different matrices of interest each one representing a
band-specific power spectrum. Finally, I average the power over the
frequencies of each band in order to obtain the estimation of the power in
that band. In the latter case, according to my understanding, I should
apply the baseline-correction after computing the average power of each
frequency-band, so that the relative "band specific power" in each time bin
is the ratio between the power averaged over all the frequencies belonging
to that band and the power averaged over all the same frequencies in the
baseline period. I would like to know if the procedure is correct and how
to implement it in fieldtrip. I am going to check ft_freqbaseline as you
kindly suggested me.
Thank for the help
Best
Marta

Il giorno lun 14 set 2020 alle ore 16:00 Stephen Whitmarsh <
stephen.whitmarsh at gmail.com> ha scritto:

> Hi Marta,
>
> It's not clear from your question whether you do or do not want to
> baseline correct power before plotting - with which I assume you mean not
> doing it in the plotting functions but instead creating a data structure
> which has had baseline correction applied. If so, ft_freqbaseline is what
> you are looking for. If not, then I am afraid I do not understand that part
> of the question.
> Regarding the question whether or not you should apply a baseline
> correction, that would depend on what you want to do. "My final goal is to
> extract different frequency-bands" is not specific enough to really give an
> informed response to that.
>
> Best,
> Stephen
>
> Op ma 14 sep. 2020 om 15:32 schreef Marta Andujar <
> marta.andujar at uniroma1.it>:
>
>> Dear all,
>> I am performing a time-frequency decomposition via Morlet's Wavelet. My
>> question is very basic and it concerns the estimation of the power. I
>> went through different tutorials, and I am a bit confused about the
>> normalization. In every tutorial I saw, the normalization is implemented
>> before plotting the results.I am using the 'relative' option, so that for
>> each frequency of interest and for each time-bin, the power is expressed as
>> the ratio between the raw power and the power averaged over the baseline
>> period. However, I would like to have my TRF results expressed as relative
>> power before plotting. Is there a way to get what I am looking for? Or
>> should I write my own code in order to get the relative power? My final
>> goal is to extract different frequency-bands, and I guess that for each of
>> these I should normalize against the power averaged both over the baseline
>> period and over the frequencies defining the band of interest. Is it
>> correct?
>> Thank you in advance
>> Marta
>>
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contenute in questo messaggio di posta elettronica sono strettamente 
riservate e indirizzate esclusivamente al destinatario. Si prega di non 
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si è il legittimo destinatario dello stesso. Qualora tale messaggio sia 
stato ricevuto per errore, si prega di restituirlo al mittente e di 
cancellarlo permanentemente dal proprio computer.
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