[FieldTrip] fieldtrip Digest, Vol 141, Issue 4

[Tineke Grent-'T-Jong]

I feel something might be wrong with your input data. It is very unlikely that an eyeblink shows up with a similar amplitude across all channels. Typically, it has a topographic distribution, with smaller amplitudes the further away from the source, in this case the eyes.

Hope this helps,
Best wishes,
Tineke Grent-'t-Jong

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Today's Topics:

   1. Why does applying fastica change the form of EEG data?
      (Elif Tülay)


----------------------------------------------------------------------

Message: 1
Date: Fri, 5 Aug 2022 13:34:50 +0300
From: Elif Tülay <e.eliftulay at gmail.com>
To: FieldTrip discussion list <fieldtrip at science.ru.nl>
Subject: [FieldTrip] Why does applying fastica change the form of EEG
	data?
Message-ID:
	<CALtq08VJsc_qb2dm+cPSA=zKhW_sphCXDgEbe7ws7y5R8Yeh-g at mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

Dear Fieldtrippers,

Now, I work on EEG data which is exported from EEGlab as segmented data. I try to remove eye blinks from the data and I wonder something about ft_componentanalysis function. When I performed fastica to remove the eye blink component, I realized that it changes the form of EEG in addition to removing the related component (please see the attached files, before and after; scales are the same). I cannot understand the reason. It is not because demean application, I checked it.

Do you have any other idea? By the way, I used averaged referencing on EEGlab. Also please find the script that I used below.



cfg            = [];

cfg.method     = 'fastica';

cfg.channel       = {'all', '-VEOG'};

comp           = ft_componentanalysis(cfg, data);



cfg = [];

cfg.component = [5];

data = ft_rejectcomponent(cfg, comp, data)



Also I wonder one more thing, what is the mission of cfg.updatesens parameter in ft_ componentanalysis function?



Many thanks in advance,
Elif
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https://doi.org/10.1371/journal.pcbi.1002202


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End of fieldtrip Digest, Vol 141, Issue 4
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