[Eeglablist] Two ICA decompositions from one dataset- based on stage of working memory

[Makoto Miyakoshi]

Dear Kathleen,

> Has anyone tried to compare cluster locations between different
conditions within the same experimental session?

That's the other path which is valid but seldom tried. The technical
concern is how to make a reasonable comparisons between conditions with
non-consistent ICs. However, if a subject participates to the experiment in
separate days, the situation in data analysis is more or less the same, so
it's definitely not something prohibiting.

On the different note Kathleen, I updated the trimOutlier today and I
addressed your request to display name of channels rejected. I also added
major improvement in code so that it is now dramatically faster than before
(or, well, the former version was too damn...)

Makoto


On Thu, Jun 26, 2014 at 3:53 PM, Kathleen Van Benthem <
kathy_vanbenthem at carleton.ca> wrote:

> Hello All,
> Has anyone tried to compare cluster locations between different conditions
> within the same experimental session?
> We are interested in locating dipoles associated specifically with
> encoding versus maintenance during a working memory task, and are using
> EEGLAB to conduct ICA and then PCA to examine dipoles.
>
> Our first method did not give us much success--originally, we tried
> running ICA on the entire dataset (including both encoding and maintenance
> conditions), and epoched after ICA was run, so that we ended up with
> separate files for the two conditions, each with the same ICA weights.
>  When we ran STUDIES for each condition separately, we found the resulting
> clusters were the same between encoding and maintenance conditions,
> even though we expected differences to exist.
>
> Because we didn't experience success with this method, we are wondering
> whether it would be advisable to create two separate files for each
> participant (from the same session) BEFORE running ICA-- One file would
> contain EEG data epoched from the first condition (encoding--two seconds
> per trial), and  the second EEG data epoched from the second
> condition (maintenance--2 seconds per trial).   We would then run ICA
> *separately* for each file and look to see if there were dipoles from the
> encoding condition ICA that* consistently *were not in the
> maintenance condition ICA results (and vice versa).   We have a priori
> hypotheses of where maintenance activity would be taking place source-wise
> as compared to where encoding would be taking place.   We are wondering if
> it is advisable to compare dipoles that result from different ICA weights-
> even when they are collected from the same session and just seconds apart.
>  If there were unique sources of brain activity (dipoles) would it be
> possible, from this design, to conclude that the unique dipoles were  in
> fact associated with the different stages of the working memory task (all
> other factors being held constant)?
>
> Thanks for your thoughts on this.  We are aware that we need to make sure
> we have large enough files in order to conduct ICA in the first place.
>
> Kathleen (Kathy) Van Benthem M.H.S., B.Sc.O.T
> Carleton University, Institute of Cognitive Science,  Ph.D. Candidate, ​
>
> Sarah
> Sarah Cebulski
> PhD candidate
> Cognitive Science, Carleton University
>
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-- 
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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