[FieldTrip] freqanalysis

[Eelke Spaak]

Dear Victoria,

Those are all very good questions. It might be very beneficial for you
to go through the following tutorial once:
http://fieldtrip.fcdonders.nl/tutorial/timefrequencyanalysis I think
many of the questions you have will be answered along the way. If not
(or if you've already read the tutorial), feel free to ask of course!

Best,
Eelke

On 3 February 2014 11:15, Victoria Schröder <victorias at dsv.su.se> wrote:
> Dear Jörn,
>
> the code works but i dont know whether my data is logical and whether i
> decided to use the right method etc.
>
> My trials are pretty long (approx 30 sec but all are not the same length)
> and i am interested in beta frequency.
>
> First, it is not really clear to me whether i should use cfg.method=mtmfft
> or cfg.method=mtmconvol. As i understand ,  the latter calculates the FFT
> for shorter self-specified time windows to look at changes in power over
> time. Is that right? however, if i have more stimuli for one condition, how
> is the time component then taken into account? does mtmconvol take all
> trials of one condition and average the the power for each time window over
> all trials? Or is each trial treated seperatly?
>
> Say i would use cfg.method=mtmfft do i need to specify a cfg.tapsmofrq when
> using cfg.taper='hanning'? As i understand hanning if appropriate for lower
> freuquencies so i should use this taper to assess beta frequencies.
>
> Say i use cfg.method=mtmconvol what cfg.t_ftimwin is appropriate?
>
> Thank you a lot for the help
> Best
> Victoria
>
>
> 2014-02-03 09:19 skrev Jörn M. Horschig:
>
>> Hi Victoria,
>>
>> is there anything wrong with the code you used below? By smoothing,
>> do you refer to smoothing in the frequency domain?
>>
>> Best,
>> Jörn
>>
>>
>> On 1/30/2014 11:33 AM, Victoria Schröder wrote:
>>>
>>> Hello
>>>
>>> I am currently working on a freqanalysis as a first step to do a
>>> connectivityanalysis. I am a bit unsure about the method to use for the
>>> freqanalysis. My stimuli are very long: between 29 and 30 sec. In total i
>>> have 4 stimuli per condition and 2 seperate conditions. I am looking at the
>>> beta range so fairly low frequencies.
>>>
>>> this is my code:
>>> Am i using the right taper and method. Should i smooth the data? and if
>>> so, what should such a smoothing parameter depend on?
>>>
>>> %fourier analysis
>>> cfg=[];
>>> cfg.output='fourier';
>>> cfg.method='mtmfft';
>>> cfg.foi=[12:30];
>>> cfg.taper='hanning';
>>> cfg.keeptrials='yes';
>>> cfg.channel={'C15' 'C10' 'B23' 'B3'};
>>> frefourier=ft_freqanalysis(cfg,data_clean);
>>>
>>>
>>> %coherence analysis
>>> cfg=[];
>>> cfg.method='coh';
>>> cfg.channelcmb={'B3'  'C15'
>>>                 'B3'  'C10'
>>>                 'B23' 'C15'
>>>                 'B23' 'C10'}
>>> coherence=ft_connectivityanalysis(cfg, frefourier);
>>>
>>>
>>> Thank you very much for the suggestions!
>>> Best
>>> Victoria
>>> _______________________________________________
>>> fieldtrip mailing list
>>> fieldtrip at donders.ru.nl
>>> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>>
>>
>>
>> --
>> Jörn M. Horschig
>> PhD Student
>> Donders Institute for Brain, Cognition and Behaviour
>> Centre for Cognitive Neuroimaging
>> Radboud University Nijmegen
>> Neuronal Oscillations Group
>> FieldTrip Development Team
>>
>> P.O. Box 9101
>> NL-6500 HB Nijmegen
>> The Netherlands
>>
>> Contact:
>> E-Mail: jm.horschig at donders.ru.nl
>> Tel:    +31-(0)24-36-68493
>> Web: http://www.ru.nl/donders
>>
>> Visiting address:
>> Trigon, room 2.30
>> Kapittelweg 29
>> NL-6525 EN Nijmegen
>> The Netherlands
>>
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>
>
> --
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