[FieldTrip] partial artifact rejection for time-frequency analysis

Mariya Manahova m.manahova at gmail.com
Mon May 14 16:04:03 CEST 2018

Hi Matthias,

Perhaps you could try taking the part of the trial you want to reject and
replacing the values there with NaNs? Then you'd be able to remove the
artifact-related part of the data while keeping your trials of the same
length. I know that some FieldTrip functions can deal with NaNs, so this
may be a solution.

All the best,

On Mon, May 14, 2018 at 3:35 PM Matthias Franken <Matthias.Franken at ugent.be>

> Dear all,
> I have an EEG dataset that consists of quite long trials (>20s).
> Therefore, For artifact rejection I would like to only reject the part of
> the trial that contains the artifact, rather than throwing away the entire
> trial, and thus I will use the cfg.artfctdef.method = ‘partial’; option in
> ft_rejectartifact.
> However, this leads to some trials being cut in two shorter “trials”
> (i.e., the part before the artifact and the part after the artifact). I’m
> guessing this will lead to edge artifacts in my time-frequency analysis,
> not only at the edges of the original trials, but also at time points where
> artifacts were cut out. SO I’m not sure how to deal with this.
> I guess one option would be to perform the time-frequency analysis first,
> and afterwards cut out the artifacts, although (1) that might lead to the
> artifact smearing into data points that were not cut out, depending on the
> time window width during frequency analysis, and (2) the artifacts
> identified visually using ft_databrowser are define din ample numbers, and
> the result from ft_freqanalysis downsamples the data.
> Did anyone face similar issues or have ideas on how to get around this?
> ________________________________________
> Matthias Franken
> postdoctoral researcher
> Experimental Psychology Department
> Ghent University
> _______________________________________________
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
> https://mailman.science.ru.nl/mailman/listinfo/fieldtrip
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