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hi Steve, <br>
<br>
Thanks, sounds like a very reasonable explanation.<br>
I'm wondering whether I could use Arjen's correction for head
movement prior to ICA decomposition, but I can imagine there would
be problems with doing the regression first... I'll ask Arjen what
he thinks and post it here - if he doesn't see this before I see him
again - but I'd be curious to hear what you think as well.<br>
<br>
Thanks a lot!<br>
Vitoria<br>
<br>
<div class="moz-cite-prefix">On 10/28/2015 11:31 PM, Stephen
Politzer-Ahles wrote:<br>
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<div>Hello Vitoria,<br>
<br>
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I'm not sure, but one of my guesses would be head movement.
That is to say, if the participant moves her head an inch
(for example) then the same type of activity is going to
start appearing on different sensors, and if that movement
isn't corrected for then you can indeed start seeing what
looks like many copies of the same component. (If you've
done EEG, this is the same thing that happens when, for
example, you bring the same participant back for multiple
sessions on separate days and concatenate the datasets
together, but didn't put the cap on on exactly the same
place each time.) Do you have marker measurements you can
use to at least check how much the head was moving, and
perhaps to correct for movements over the course of the
session?<br>
<br>
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Best,<br>
</div>
Steve<br>
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---<br>
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Stephen Politzer-Ahles<br>
University of Oxford<br>
Language and Brain Lab, Faculty of
Linguistics, Phonetics & Philology<br>
<a moz-do-not-send="true"
href="http://users.ox.ac.uk/%7Ecpgl0080/"
target="_blank">http://users.ox.ac.uk/~cpgl0080/</a></span></div>
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Message: 5<br>
Date: Wed, 28 Oct 2015 20:44:26 -0700<br>
From: Vit?ria Piai <<a moz-do-not-send="true"
href="mailto:v.piai.research@gmail.com">v.piai.research@gmail.com</a>><br>
To: FieldTrip discussion list <<a
moz-do-not-send="true"
href="mailto:fieldtrip@science.ru.nl"><a class="moz-txt-link-abbreviated" href="mailto:fieldtrip@science.ru.nl">fieldtrip@science.ru.nl</a></a>><br>
Subject: [FieldTrip] many ICA components looking
the same<br>
Message-ID: <<a moz-do-not-send="true"
href="mailto:5631961A.1050507@gmail.com">5631961A.1050507@gmail.com</a>><br>
Content-Type: text/plain; charset="utf-8";
Format="flowed"<br>
<br>
Hi everyone,<br>
<br>
I'm running ICA (cfg.method = 'runica') on CTF
data with 274 sensors. I<br>
was restricting my decomposition to 80 components
at first, and it<br>
worked well for all previous patients.<br>
Somehow, for this particular patient, many of the
components have<br>
similar topography (I'm only showing till 42 below
but the similarity<br>
continues for more components). Has anyone ever
seen this before?<br>
If I look at the time course of these components,
not all of them are<br>
clear eye-movements, but according to the
topography, you'd think they are.<br>
Any thoughts, like either changing the method or
rejecting only those<br>
components whose time courses clearly indicate eye
movements and keep<br>
other components despite their topographies?<br>
<br>
Thanks,<br>
Vitoria<br>
<br>
<br>
<br>
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