[FieldTrip] partial artifact rejection for time-frequency analysis

[Mariya Manahova]

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,
Marisha

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

> 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
>
>
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> fieldtrip at donders.ru.nl
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