[FieldTrip] automatic artifact correction after virtual channels/beamformer

Tue Apr 15 09:03:00 CEST 2014

Hi Haiteng,

Basically the automatic artefact detection algorithms removes some EEG (if artefactual) and splits the data into two trials. These trials are not the same size.

TRENTOOL can only work on trials that are the same length. So I determined what the biggest trial length was and redefined the trials.

ie cfg = []

    cfg.length = x length

    ft_redefinetrial( cfg, data)

However this is causing computational errors later on. So I was wondering whether you could append the trials together and place a discontinuation marker between them.

The other thing I tried was to pass in the argument 'nan' into the reject artefact function, but then this causes an issue with the virtual channel procedure.

Tyler

*************************

Tyler Grummett ( BBSc, BSc(Hons I))
PhD Candidate
Brain Signals Laboratory
Flinders University
Rm 5A301
Ext 66124
________________________________
From: fieldtrip-bounces at science.ru.nl <fieldtrip-bounces at science.ru.nl> on behalf of Haiteng Jiang <haiteng.jiang at gmail.com>
Sent: Monday, 14 April 2014 9:04 PM
To: fieldtrip at science.ru.nl
Subject: Re: [FieldTrip] automatic artifact correction after virtual channels/beamformer

Hi  Tyler ,
          I think it makes sense to apply  the inverse spatial filter on the  the marked out data  since you build it on this interval.  In other words, non-marked out  intervals   data has different  inverse filter.  I don't understand  appending  trials after  automatic artefact   detection.  Do you mean keep trials after automatic artefact   detection ?

                                                                 Best,
                                                                 Haiteng

Message: 3
Date: Mon, 14 Apr 2014 07:26:44 +0000
From: Tyler Grummett <tyler.grummett at flinders.edu.au<mailto:tyler.grummett at flinders.edu.au>>
To: FieldTrip discussion list <fieldtrip at science.ru.nl<mailto:fieldtrip at science.ru.nl>>
Subject: Re: [FieldTrip] automatic artifact correction after    virtual
        channels/beamformer
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Hello Haiteng,

Thankyou for the response. Yes I have gone through the tutorial. I use clean data to make the inverse spatial filter. But do then apply it to

marked out data or can apply it to non-marked out data. Also, is there a way to append trials after you run an automatic artefact

rejection algorithm over it? At the moment, I am trying to use a function that requires equal trial lengths. I can use ft_redefinetrial

to grab a 2 second epoch from each 'trial'. However that feel a little crude as I am throwing out a lot of data.

Your help will be greatly appreciated.

Tyler

*************************

Tyler Grummett ( BBSc, BSc(Hons I))
PhD Candidate
Brain Signals Laboratory
Flinders University
Rm 5A301
Ext 66124
________________________________
From: fieldtrip-bounces at science.ru.nl<mailto:fieldtrip-bounces at science.ru.nl> <fieldtrip-bounces at science.ru.nl<mailto:fieldtrip-bounces at science.ru.nl>> on behalf of Haiteng Jiang <haiteng.jiang at gmail.com<mailto:haiteng.jiang at gmail.com>>
Sent: Monday, 14 April 2014 3:53 PM
To: fieldtrip at science.ru.nl<mailto:fieldtrip at science.ru.nl>
Subject: Re: [FieldTrip] automatic artifact correction after virtual channels/beamformer

Hi Tyler,
   It is always nice to computate virtual MEG channels based on artifact-corrected  CLEAN data .  Note that  we use clean data to get the inverse spatial filter by DICS.  Regrading  to how to create virtual channel , please have a look at tutorial: http://fieldtrip.fcdonders.nl/tutorial/shared/virtual_sensors

                                                             Best,
                                                             Haiteng

Message: 2
Date: Mon, 14 Apr 2014 02:54:16 +0000
From: Tyler Grummett <tyler.grummett at flinders.edu.au<mailto:tyler.grummett at flinders.edu.au><mailto:tyler.grummett at flinders.edu.au<mailto:tyler.grummett at flinders.edu.au>>>
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Subject: [FieldTrip] automatic artifact correction after virtual
        channels/beamformer
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?Hello all,

I was just wondering whether it is necessary to use the artifact corrected data when creating virtual channels from beamformer sources

or whether you are able to use original, non-artifact corrected data.

Tyler

*************************

Tyler Grummett ( BBSc, BSc(Hons I))
PhD Candidate
Brain Signals Laboratory
Flinders University
Rm 5A301
Ext 66124
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--
Haiteng Jiang
PhD candidate
Neuronal Oscillations Group
Donders Institute for Brain, Cognition and Behaviour
Centre for Cognitive Neuroimaging
Radboud University Nijmegen

Visiting address
Room 2.32
Donders Centre for Cognitive Neuroimaging
Kapittelweg 29
6525 EN  Nijmegen
the Netherlands

 Tel.: +31 (0)243668291<tel:%2B31%20%280%29243668291>
 Web:  https://sites.google.com/site/haitengjiang/
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End of fieldtrip Digest, Vol 41, Issue 25
*****************************************

--
Haiteng Jiang
PhD candidate
Neuronal Oscillations Group
Donders Institute for Brain, Cognition and Behaviour
Centre for Cognitive Neuroimaging
Radboud University Nijmegen

Visiting address
Room 2.32
Donders Centre for Cognitive Neuroimaging
Kapittelweg 29
6525 EN  Nijmegen
the Netherlands

 Tel.: +31 (0)243668291
 Web:  https://sites.google.com/site/haitengjiang/
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