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

Herring, J.D. (Jim) j.herring at fcdonders.ru.nl
Mon Jun 17 14:23:13 CEST 2013

Dear Karen,


Comparing the BVA and Fieldtrip images it seems that the trials in BVA
have been filtered using at least a high-pass filter. I can see from the
BVA image that you have applied filters prior to averaging your trials.
>From the Fieldtrip code you've posted I cannot see any filtering applied.
If you could find out what filters were applied to the trials in BVA and
apply the same filters to the trials in FieldTrip using ft_preprocessing
your results will most likely be the same.






From: fieldtrip-bounces at science.ru.nl
[mailto:fieldtrip-bounces at science.ru.nl] On Behalf Of Karen Schuil
Sent: maandag 17 juni 2013 13:56
To: fieldtrip at science.ru.nl
Subject: [FieldTrip] ERP average Brain Vision is different from ERP
average FieldTrip


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


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,











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