[FieldTrip] Optimal settings for ft_artifact_zvalue for detecting electrode pops

[Jan Ostrowski]

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
--

_____________________________________________________________________

Universitätsklinikum Hamburg-Eppendorf; Körperschaft des öffentlichen Rechts; Gerichtsstand: Hamburg | www.uke.de
Vorstandsmitglieder: Prof. Dr. Christian Gerloff (Vorsitzender), Joachim Prölß, Prof. Dr. Blanche Schwappach-Pignataro, Matthias Waldmann (komm.)
_____________________________________________________________________

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