[FieldTrip] Beamforming analysis in frequency band, concept problem

Tue Mar 27 12:46:35 CEST 2012

```Thank you Stephan, just one thing, why i need a time window big enough? so
i'm just studying the frequency.

Best,

Mikel

2012/3/27 Stephan Moratti <smoratti at psi.ucm.es>

> Dear Mikel,
>
> I understand that you should do a mtmfft with a center frequency of
> interest (in your case cfg.foil = [11 11]) and then you do a frequency
> smoothing of 3 Hz (cfg.tapsmofrq = 3). Of course you need a time window big
> enough to allow such a smoothing. The CSD should represent a frequency
> window of 8 to 14 Hz then. Then you put the result of the mtmfft into the
> dics beamformer.
>
> Best,
>
> Stephan
>
> El 27/03/2012, a las 11:19, Ion Lavado escribió:
>
> Hello, i'm having problems trying the beamformer analysis with a frequency
> band of interest. I would like to have for example an interval like [8 14]
> Hz. My concept problem is about the cfg.frequency and
> cfg.tapsmofrq  values. (it must be a escalar, but i want a frequency band).
>
> %FREQ ANALYSIS
> cfg = [];
> cfg.method    = 'mtmfft';
> cfg.output    = 'powandcsd';
> cfg.tapsmofrq = 5;
> cfg.foilim    = [8 14];
> freq_words_alpha = ft_freqanalysis(cfg, words);
>
>
> %SOURCE ANALYSIS
> cfg              = [];
> cfg.frequency    = 11;
> cfg.lambda=0;
> cfg.method       = 'dics';
> cfg.coordsys       = 'neuromag';
> cfg.projectnoise = 'yes';
> cfg.channel   = {'MEG'};
> cfg.grid         = grid;
> cfg.reducerank      = 2;
> cfg.vol          = vol02;
> vol02=ft_convert_units(vol02,'cm');
> source_pre11  = ft_sourceanalysis(cfg,  freq_words_alpha );
>
>
> I use a cfg.frequency of 11 but i don't have really clear what i'm doing
> as a get the same result using cfg.frequency=11 but a freqanalysis in [10
> 12]. I would be very grateful if someone could solve my doubt.
>
> Best wishes,
>
> Mikel
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>
>
> ________________________________________________________
> Stephan Moratti, PhD
>
>
> Departamento de Psicología Básica I
> Campus de Somosaguas
> 28223 Pozuelo de Alarcón (Madrid)
> Spain
>
> and
>
> Center for Biomedical Technology
> Laboratory for Cognitive and Computational Neuroscience
> Campus Montegancedo
> 28223 Pozuelo de Alarcón (Madrid)
> Spain
>
>
> email: smoratti at psi.ucm.es
> Tel.:    +34 679219982
>
>
>
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