[FieldTrip] Redoing Brain Vision Analyzer in Field Trip

Tzvetan Popov tzvetan.popov at uni-konstanz.de
Thu Nov 13 11:13:43 CET 2014


Dear Gerome,

one thing you could change is keep the reference the same in both cases. So far you are referencing the data against the mastoids in BVA and a common reference in FieldTrip.
This is a potential source of variance in the waveforms you’ll get. 

best
tzvetan


> Hello All, 
> 
> I would like some help to  replicate an analysis done in brain vision analyzer in field trip. Here is the details of the analysis in brain vision. I have done most of the code but I get almost completely different results which is puzziling. Maybe some of the filteres are not defined properly- so if anyone has some time I would appreciate the help :-)
> 
> 
> Thanks alot,
> Gerome
> 
> Here is the brain vision sequence I am trying to replicate
>   - Read in Data
>  - Reference to mastiod
>  - 100Hz Band rejection filter - bandwidth 8, slope 2
>  - High cuttoff (low pass filter at 45Hz with a slope of 24dB/oct)
>  - Low cuttoff (high pass filter at 0.53Hz, time constant 0.3002923, 24db/ oct)
>  - Notch Filter at 50Hz
>  - Segmentation
>  - Baseline Correction -200 ms to - 5 ms
>  - Averaging segments
> 
> 
> 
> Here is my Field trip code: 
> 
> %rereference all trials
> cfg.reref = 'yes';
> cfg.continuous = 'yes';
> 
> % reference what channels
> cfg.channel = 'all';
> %choose the reference channel
> cfg.refchannel = {'EXG1' 'EXG2'};
> 
> % cfg.dataset = 'CVP1S1.bdf';
> cfg.continuous = 'yes';
> %
> 
> %bandfilter
> cfg.bsfilter = 'yes';
> cfg.bsfiltord = 2;
> % cfg.bsfiltdir = 'onepass-zerophase';
> cfg.bsfreq = [92 108];
> 
> 
> % 
> %DFT
> cfg.dftfilter = 'yes';
> 
> % IIR Filters
> cfg.lpfilter = 'yes';
> cfg.lpfilttype  = 'but';
> % cfg.lpfiltdir = 'onepass-zerophase';
> cfg.lpfreq  = 45;
> 
> cfg.hpfilter = 'yes';
> cfg.hpfilttype  = 'but';
> % cfg.hpfiltdir = 'onepass-zerophase';
> cfg.hpfreq  = 0.53;
> 
> data = ft_preprocessing(cfg);
> 
> 
> % Define Trial
> cfg = [];
> cfg.trialdef.eventtype  = 'STATUS';
> cfg.dataset = eeg_file;
> cfg.trialdef.eventvalue = 65522;
> cfg.trialdef.prestim    = 0.2;
> cfg.trialdef.poststim   = 0.3;
> cfg = ft_definetrial(cfg);
> 
> data_vep = ft_redefinetrial(cfg, data);
> 
> % Baseline Correction
> cfg = [];
> cfg.demean = 'yes';
> cfg.baselinewindow = [-0.2 -0.05];
> data_vep = ft_preprocessing(cfg, data_vep);
> 
> %Averaging
> cfg=[];
> avg_data = ft_timelockanalysis(cfg, data_vep);
> 
> 
> cfg.ylim = [-10 10];
> cfg.channel = 'O1';
> 
> ft_singleplotER(cfg,avg_data);
> 
> -- 
> _____________________
> Gerome Manson PhD Student
> Laboratoire de Neuroscience Cognitives- Aix Marseille Université
> Perceptual Motor Behavior lab- University of Toronto
> gerome.manson at utoronto.ca
> gerome.manson at univ-amu.fr
> 416-978-6109
> 
> _______________________________________________
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip

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