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

[Karen Schuil]

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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