[FieldTrip] Redoing Brain Vision Analyzer in Field Trip

[Tzvetan Popov]

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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