[FieldTrip] Automatic artifact detection (no rejection)

Philipp Taesler p.taesler at uke.de
Fri Jul 1 14:10:09 CEST 2016

Hi Robin,

you are right, the comment in the function explicitly says:

% Contrary to the other artifact detection functions, this function
% will mark the whole trial as an artifact if the threshold is exceeded.
% Furthermore, this function does not support artifact- or filterpadding.

I didn't know that. Hmmm, then I guess your only option is to either
visually review the marked trials and unmark the ones you want to keep.
Another possibilty might be to use ft_redefinetrial to create a dataset
with shorter trials, run the rejection on this data, and use the
resulting artefact definitions for your original data. (Not sure if that
is straightforward, since I never did this myself).


Am 01.07.2016 um 13:45 schrieb Robin Kramer:
> Hi Steve and Phil,
> Thank you, that is exactly what I was looking for. However, it seems as
> if it not yet implemented in ft_artifact_threshold(). I see no
> difference between the amount of rejected trials. Moreover, the option
> is not specified on the reference page, though it is on ft_artifact_eog
> for instance. Is that correct?
> Best,
> Robin
> 2016-07-01 12:25 GMT+02:00 Stephen Politzer-Ahles
> <stephen.politzer-ahles at ling-phil.ox.ac.uk
> <mailto:stephen.politzer-ahles at ling-phil.ox.ac.uk>>:
>     Hi Robin,
>     Rather than deselecting certain trials, it sounds like what you'd
>     want to do is just not mark a trial 'bad' at all if the artifact is
>     outside your time window of interest. For this, I think negative
>     trial-padding
>     (http://www.fieldtriptoolbox.org/tutorial/automatic_artifact_rejection#negative_trialpadding)
>     should be able to do what you need.
>     Best,
>     Steve
>     ---
>     Stephen Politzer-Ahles
>     University of Oxford
>     Language and Brain Lab
>     Faculty of Linguistics, Phonetics & Philology
>     http://users.ox.ac.uk/~cpgl0080/
>         Message: 3
>         Date: Fri, 1 Jul 2016 11:53:06 +0200
>         From: Robin Kramer <kramerrobin92 at gmail.com
>         <mailto:kramerrobin92 at gmail.com>>
>         To: fieldtrip at science.ru.nl <mailto:fieldtrip at science.ru.nl>
>         Subject: [FieldTrip] Automatic artifact detection (no rejection)
>         Message-ID:
>         <CAHnFAUi9soOTkJvq6hLtHNn8cUfUgvSHuGP7zJuO8=X_1c4fPQ at mail.gmail.com
>         <mailto:X_1c4fPQ at mail.gmail.com>>
>         Content-Type: text/plain; charset="utf-8"
>         Hi all,
>         I want to use automatic artifact detection to easily find the
>         trials where
>         range-thresholds may be exceeded. However, because the segments
>         are a
>         little larger than the time of interest (for baseline correction
>         a.o.), I
>         do not always want to remove all the trials where the threshold is
>         exceeded. Is there a way to deselect the automatically detected
>         artifacts?
>         Best,
>         Robin Kramer

Philipp Taesler
Department of Systems Neuroscience
University Medical Center Hamburg-Eppendorf
Martinistr. 52, W34, 20248 Hamburg, Germany

Phone: +49-40-7410-59902
Fax:   +49-40-7410-59955
Email: p.taesler at uke.de


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