[FieldTrip] Beamforming analysis in frequency band, concept problem

[Stephan Moratti]

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.grad            =  freq_words_alpha.grad;
> 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

see also: http://web.me.com/smoratti/

Universidad Complutense de Madrid
Facultad de Psicología
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
Parque Científico y Tecnológico de la Universidad Politecnica de Madrid
Campus Montegancedo
28223 Pozuelo de Alarcón (Madrid)
Spain


email: smoratti at psi.ucm.es
Tel.:    +34 679219982


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