[Eeglablist] eeglablist Digest, Vol 100, Issue 28

Thu Feb 21 01:19:15 PST 2013

Dear all

I have 14 channel eeg recorded data from emotiv epoc. It is  continuous
data in edf  format using Test bench and I want to remove artifact from it
using ICA. I follow  A12 Quick Tutorial Rejection & chapter 09- decomposing
data using ICA from wiki tutorial.
I am using eeglab v 12.0.1.0.b. some function are disable during analysis
of data. like Automatic epoch rejection, reject data epochs etc. And after
running ICA only one function is enable i.e Tools>Reject Data using ICA>
Reject component by maps.
when i am rejecting component and run second ICA. data gets reduced.

so kindly answer the following questions & suggest me easy way for data
analysis of continuous eeg as soon as possible.

1. Is it neccesary to extract data epochs & why ??
2. After running ICA how can i get eeg data back..??
3. why are these function disable. specially Tools>Reject data using
ICA> *Reject
data (all method)* & Tools>* reject data epoch> reject data (all method) *
bold letter function are disable.

Regards
Neelam Sharma

On Wed, Feb 20, 2013 at 11:19 PM, <eeglablist-request at sccn.ucsd.edu> wrote:

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> Today's Topics:
>
>    1. Standardize electrodes montage for group analysis
>       (Iman M.Rezazadeh)
>    2. Re: running ICA a second time (Tarik S Bel-Bahar)
>    3. Re: Standardize electrodes montage for group analysis
>       (Chadwick Boulay)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 19 Feb 2013 16:47:08 -0800
> From: "Iman M.Rezazadeh" <irezazadeh at ucdavis.edu>
> Subject: [Eeglablist] Standardize electrodes montage for group
>         analysis
> To: <eeglablist at sccn.ucsd.edu>
> Message-ID: <00e501ce0f03$d0364860$70a2d920$@ucdavis.edu>
> Content-Type: text/plain; charset="utf-8"
>
> Dear all,
>
> Since each subject has its own head diameter thus electrode placement over
> the head might be slightly different !
>
> Thus, do you have any idea how to standardize the electrode configuration
> from different subjects for within or btw group comparison!
>
> I am using spline interpolation to convert my 128 channel data to 81
> channel. However the new coordinates are still slightly different from
> subject to subject!
>
>
>
> Any thought???
>
>
>
> Iman M.Rezazadeh, PhD
>
> Postdoctoral Research Fellow
>
> Center for Mind and Brain
>
> University of California, Davis
>
>  <http://www.linkedin.com/pub/iman-m-rezazadeh/10/859/840>
> www.linkedin.com/pub/iman-m-rezazadeh/10/859/840
>
>  <http://mindbrain.ucdavis.edu/people/imanmr>
> http://mindbrain.ucdavis.edu/people/imanmr
>
> email :  <mailto:irezazadeh at ucdavis.edu> irezazadeh at ucdavis.edu
>
> Tel: 530-297-4444
>
> Cell:310-490-1808
>
> Skype: Imanmr
>
> ????? ???? ???????
>
> ???????
>
>
>
>
>
>
>
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> Message: 2
> Date: Tue, 19 Feb 2013 20:01:03 -0500
> From: Tarik S Bel-Bahar <tarikbelbahar at gmail.com>
> Subject: Re: [Eeglablist] running ICA a second time
> To: Veerle ROSS <veerle.ross at uhasselt.be>
> Cc: "eeglablist at sccn.ucsd.edu" <eeglablist at sccn.ucsd.edu>
> Message-ID:
>         <CABCAK+hyJeONgdRHVx==
> ReN3EM+55YnaNevnY7jpaO3U5EXMqQ at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Greetings Ross:
>
> Some brief responses to your questions below, I hope they are helpful. I've
> numbered the responses according to your questions.
>
> 0. if you have note please search eeglab list archives where you will
> definitely find some past discussions.
> PLease read through the articles about cleaning with eeglab, which you can
> easily find on Google Scholar.
> Check out the eeglab tutorial and wiki, particular guidelines.
>
> 1a. You can use PCA (see post within last 2 months on this subject based on
> a "should I PCA and if so what is best method")
> Reducing by PCA may decrease the "validity" or "truthfullness" of your ICs.
> Check Joseph Dien's PCA toolkit for some principled methods to do PCA.
>
> 1c. You should find similar ICs after 2 ICAs, as the second ICA
> decomposition. The ones in the second ICA should be cleaner and more
> accurate.
> Some people just publish their first ICA results, as it is not always the
> case that you gain much from a second ICA.
>
> 2a. I assume you have properly cleaned your data before the first ICA.
> My recommendation is, if you want to do a second ICA, first consider doing
> what eeglab documentation recommend:
> after your first ICA, then do artifactual epoch rejection using ICA-based
> rejection, then do a second ICA.
>
> 2b. it's not clear what your question is, perhaps there is a word missing
> in your question.
> You could remove noisy or blink or other artifactual components if you want
> to, go ahead
> and do a second ICA, and compare the results to doing it via the method
> suggested in the response to 2a above.
>
> also:
> Check out the the ADJUST plugin (amongst others for a variety of cleaning
> techniques).
> &
> Note there are least three camps:
> a. those who use ICA just to deblink or otherwise clean their data, and
> then they reconstruct the EEG and do their analyses outside of ICA space.
> [ergo, ICA is a cleaning tool]
> b. those who use ICA to get ICs that reflect brain dynamics and (often)
> established ERP components, they do their analyses on ICs [ergo, ICA gives
> real brain dynamics]
> c. those who use PCA (with or without ICA) to decompose ERPs into spatial
> (and/or) temporal components, they do their analyses on PCs
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> ------------------------------
>
> Message: 3
> Date: Wed, 20 Feb 2013 11:36:14 +0900
> From: Chadwick Boulay <boulay at bme.bio.keio.ac.jp>
> Subject: Re: [Eeglablist] Standardize electrodes montage for group
>         analysis
> To: eeglablist at sccn.ucsd.edu, "Iman M.Rezazadeh"
>         <irezazadeh at ucdavis.edu>
> Message-ID: <5124369E.7000804 at bme.bio.keio.ac.jp>
> Content-Type: text/plain; charset="iso-8859-1"
>
> I think the assumption is that if brain A is 10% larger than brain B
> then the cortical region normally associated with C3 is 10% further from
> the midline in brain A than it is in brain B. Thus, if you are using
> differently-sized caps (with different electrode spacing) for
> differently-sized heads then you may assume that C3 from subject A
> represents approximately the same patch of brain as C3 from subject B.
> The precise coordinates of C3 don't matter.
>
> Of course the above assumption is false not only because the head shapes
> vary but also because the relative skull conductance and brain
> curvatures vary. While having super-accurate coordinates might help
> overcome the problem of head shape, it won't help with the other
> problems. If you have anatomical MR images for each subject and you are
> able to coregister your electrode positions with the MRI then you may be
> able to use ICA+NFT+DIPFIT to identify subject-specific neurobiological
> 'sources'. You may then use some component-clustering algorithm to
> figure out which component from each subject represents a particular
> patch of brain then do your between subject/group comparisons on those
> components' activations. (Notice that I skipped over the
> skull-conductance problem.)
>
> If you need to identify precise (not necessarily accurate) brain regions
> associated with your task then the above method might be for you.
> However, if you REALLY need to identify brain sources accurately then
> you might be better off going with fMRI or EEG-fMRI if time-resolution
> is important.
>
> If you don't need to report specific brain regions then I'd just stick
> with averaging across electrodes with the same name.
>
> On 2/20/2013 9:47 AM, Iman M.Rezazadeh wrote:
> >
> > Dear all,
> >
> > Since each subject has its own head diameter thus electrode placement
> > over the head might be slightly different !
> >
> > Thus, do you have any idea how to standardize the electrode
> > configuration from different subjects for within or btw group comparison!
> >
> > I am using spline interpolation to convert my 128 channel data to 81
> > channel. However the new coordinates are still slightly different from
> > subject to subject!
> >
> > Any thought???
> >
> > Iman M.Rezazadeh, PhD
> >
> > Postdoctoral Research Fellow
> >
> > Center for Mind and Brain
> >
> > University of California, Davis
> >
> > www.linkedin.com/pub/iman-m-rezazadeh/10/859/840
> > <http://www.linkedin.com/pub/iman-m-rezazadeh/10/859/840>
> >
> > http://mindbrain.ucdavis.edu/people/imanmr
> >
> > email : irezazadeh at ucdavis.edu <mailto:irezazadeh at ucdavis.edu>
> >
> > Tel: 530-297-4444
> >
> > Cell:310-490-1808
> >
> > Skype: Imanmr
> >
> > ????? ???? ???????
> >
> > ??*?*????
> >
> > /-- The information contained in this message is intended only for the
> > recipient, and may be a confidential communication or may otherwise be
> > privileged and confidential and protected from disclosure. If the
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