[FieldTrip] ft_preproc_hilbert questions
mcantor at umich.edu
Tue Oct 28 20:48:03 CET 2014
Ah, so if I do a narrow BP filter around a single frequency, looped over
however many frequencies I want, and then restructure the looped data into
a dimensionally similar matrix as powspctrm in a fieldtrip-type structure,
I could effectively turn it into a TFR?
On Tue, Oct 28, 2014 at 3:05 PM, Rodrigo Montefusco <
rmontefusco at med.uchile.cl> wrote:
> Hi Max,
> to what I understand, the output of Hilbert will be the amplitude of the
> input signal (envelope). If you want to use that information, then the only
> step you should add before is a very good and sweet narrow band filter (as
> narrow as you want your frequency bins). Then, the filter design is the
> hard part, because you need a filter that is able to filter out other
> frequencies without introducing any kind of artifact.
> Hopefully someone else has something to add, or if I'm missing any stuff.
> On Tue, Oct 28, 2014 at 2:16 PM, Max Cantor <mcantor at umich.edu> wrote:
>> So this is not a specific method-based question, but something more
>> I've been slowly reading through bits and pieces of Mike Cohen's
>> 'Analyzing Neural Time Series Data' book, in an attempt to gain a better
>> understanding of how things like Fourier Transform, Wavelets, and Hilbert
>> work on a more fundamental level.
>> Fieldtrip does not have a built in Hilbert time frequency analysis (that
>> I'm aware of), but from having read through that chapter of Cohen's book
>> I've been able to effectively create a hilbert analysis of my own.
>> However, I was wondering if it would be possible to use
>> ft_preproc_hilbert (setting cfg.hilbert = 'complex', 'real', etc. in
>> ft_preprocessing) to do this in a more efficient and fieldtrip-compatible
>> way. It seems I can use this setting to get the analytic signal, phase,
>> power, and other things, but since this is on raw/epoched data, there is no
>> obvious way I can think of to apply a time or frequency series as in the
>> other TFRs. It seems I could either write a fieldtrip function from
>> scratch, which I'm not prepared to do, or write a function to reformat
>> fieldtrip data to work using the Cohen function, and then output it back
>> into a fieldtrip function, which would be fine but I'm more interested to
>> know if the ft_preproc_hilbert function can do what I want more efficiently.
>> *So boiling it down**, my questions are:*
>> 1. Can cfg.hilbert parameter for ft_preprocessing (or ft_preproc_hilbert
>> called directly) be used as an ad hoc hilbert TFR, and if so what ad hoc
>> steps would one need to take?
>> 2. If it cannot be used this way, what situations is it meant for?
>> Max Cantor
>> Lab Manager
>> Computational Neurolinguistics Lab
>> University of Michigan
>> fieldtrip mailing list
>> fieldtrip at donders.ru.nl
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
Computational Neurolinguistics Lab
University of Michigan
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