[FieldTrip] Optimal settings for ft_artifact_zvalue for detecting electrode pops

[Schoffelen, J.M. (Jan Mathijs)]

Hi Jan,

I think that the morphology of an electrode pop looks a bit like a (low amplitude) eye blink (but then occurring at an isolated electrode, not necessarily a frontal one). In that context, I would imagine that a sequence of processing steps that highlight eyeblinks might also detect the larger pops.

Good luck,
Jan-Mathijs


On 30 Jan 2024, at 12:19, Jan Ostrowski via fieldtrip <fieldtrip at science.ru.nl<mailto:fieldtrip at science.ru.nl>> wrote:


Dear Fieldtrippers,

I was wondering whether you could provide some advice on the optimal configuration for ft_artifact_zvalue function so that it might more or less reliably detect electrode pop artifacts. When I talk about electrode pops, I mean those artifacts with a very sharp, high amplitude onset and a subsequent gradual decay. (We use EEG, not MEG)

I have been trying the configuration for detecting SQUID jumps as suggested on the corresponding tutorial page, but I realized SQUID jumps look quite different than electrode pops, especially after the initial sharp onset.

My approach is to use ft_artifact_zvalue to generate sample markers for the artifacts, and then use ft_rejectartifact with the preprocessed data loaded into the workspace to remove those trials.

This has been my configuration so far:

% +++ Jump artifact config +++
cfgJump = [];
cfgJump.continuous   = 'no';
% channel selection, cutoff and padding
cfgJump.artfctdef.zvalue.channel = target_chn;
cfgJump.artfctdef.zvalue.cutoff  = 60;
cfgJump.artfctdef.zvalue.trlpadding = 0;
cfgJump.artfctdef.zvalue.artpadding = 0;
cfgJump.artfctdef.zvalue.fltpadding = 0;
% algorithmic parameters
cfgJump.artfctdef.zvalue.cumulative = 'yes';
cfgJump.artfctdef.zvalue.medianfilter = 'yes';
cfgJump.artfctdef.zvalue.medianfiltord = 9;
cfgJump.artfctdef.zvalue.absdiff = 'yes';

I appreciate any help on this!

Cheers,
Jan Ostrowski


--
Jan Ostrowski, M.Sc.
Department of Systems Neuroscience
University Medical Center Hamburg-Eppendorf
Martinistr. 52
Building W34, Room 320b
D-20246 Hamburg, Germany

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