[FieldTrip] ERP average Brain Vision is different from ERP average FieldTrip

[Aaron Schurger]

To me it really looks like BVA is applying a high-pass filter at some
stage. When you export the data, the high-pass filter has probably
already been applied. It is typical in EEG (though not a good idea in
my opinion) to apply a high-pass filter with a cutoff at around 0.05
or 0.1 Hz. There should be a setting somewhere in BVA to turn off the
high-pass filter. Anyway, that's my guess just from looking at the
figure you attached.
Cheers,
Aaron

On Mon, Jun 17, 2013 at 1:56 PM, Karen Schuil <karenschuil at gmail.com> wrote:
> Dear Fieldtrip Users,
>
> I have a BVA-Fieldtrip problem. The average ERPs of Brain Vision Analyser
> are different from the ERPS of FieldTrip. It seems that in Fieldtrip a slow
> negative drift is added and peaks are more/less pronounced than in BVA
> (attached is a picture of the two different plots).
>
> An expert FieldTrip User and I could not find a solution for this problem. I
> hope one of you has a suggestion for this problem.
>
> The individual trial data was exported from BVA (version 2.02.5859) with the
> following settings:
> File extension: .seg
> Write header file: yes
> Write marker file: yes
> Format: BINARY
> Orientation: MULTIPLEXED
> Line Delimiter: CRLF (PC style)
> Binary format: 16-Bit signed integer format
> Set resolution manually: no
> Individually optimized resolution for each channel: yes
> Convert to big-endian order: no
> Export all channels: no
> Export the following channels:
> AF3 AF4 AF7 AF8 AFz C1 C2 C3 C4 C5 C6 CP1 CP2 CP3 CP4 CP5
> CP6 CPz Cz F1 F2 F3 F4 F5 F6 F7 F8 FC1 FC2 FC3 FC4 FC5
> FC6 FCz Fpz FT7 FT8 Fz Iz O1 O2 Oz P1 P10 P2 P3 P4 P5
> P6 P7 P8 P9 PO3 PO4 PO7 PO8 POz Pz T7 T8 TP7 TP8
> Created Using Component Version 2.0.2.5827
>
> We used Matlab version 7.10.0 R2, and fieldtrip version 13-06-2013 (and
> tried a version from 2011).
>
> The scripts we used are read_analyzer_data and timelockanalysis. This is the
> code we used for calling the scripts:
> % read data into fieldtrip
> cfg = [];
>
> cfg.inputfile = 'pp10_A';
> cfg.triggercode = 'S 20';
> cfg.triggertype = 'Stimulus';
> cfg.prestim = 1.2;
> cfg.poststim = 1.7;
>
> pp10_l = read_analyzer_data(cfg);
>
> % check: compute ERP
> %
> cfg = [];
> pp10_ERP = timelockanalysis(cfg, pp10_l);
>
> %plot ERP
>
> cfg = [];
> cfg.layout = 'elec1010.lay';
> cfg.xlim = [-0.15 1.7];
> cfg.ylim = [-12.25 12.25];
> % cfg.baseline = 'yes';
> % cfg.baselinetype = 'absolute';
> cfg.showlabels = 'yes';
> cfg.interactive = 'yes';
>
> multiplotER(cfg, pp10_ERP);
>
>
> I hope you can help!
>
> Kind regards,
> Karen
>
>
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>
> _______________________________________________
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip



-- 
Aaron Schurger, PhD
Post-doctoral researcher
INSERM U992 / NeuroSpin
CEA - Saclay, France
+33-1-69-08-66-47
aaron.schurger at gmail.com
http://www.unicog.org