[Eeglablist] Artifacts after removal of ICA component

[Eric HG]

Thanks a lot for the responses!

How would you go about extracting N-1 components? I can't see it under
pop_runica.

Best,

Eric

On Sat, Dec 10, 2016 at 8:49 AM, Iman Mohammad-Rezazadeh <
irezazadeh at ucdavis.edu> wrote:

> You may want to see https://sccn.ucsd.edu/pipermail/eeglablist/2014/
> 007810.html
>
> -Iman
>
>
>
> *-------------------------------------------------------------*
>
> *Iman M.Rezazadeh, Ph.D*
>
> Semel Intitute, UCLA , Los Angeles
>
> & Center for Mind and Brain, UC DAVIS, Davis
>
>
>
>
>
>
>
> *From:* eeglablist-bounces at sccn.ucsd.edu [mailto:eeglablist-bounces@
> sccn.ucsd.edu] *On Behalf Of *Ahmad, Jumana
> *Sent:* Friday, December 9, 2016 10:02 AM
> *To:* Eric HG <erichg2013 at gmail.com>; eeglablist <eeglablist at sccn.ucsd.edu
> >
> *Subject:* Re: [Eeglablist] Artifacts after removal of ICA component
>
>
>
> Hi Eric,
>
> Did you reduce the rank of your data by 1 before running ICA? I would do
> Matlab rank(EEG.data(:,:)) and check it is not 1 less than the number of
> your channels in ICA. If it is the same and you are not rank deficient. If
> you are then you can perform channel rejection to match EEG.nbchan with
> rank(EEG.data(:,:)).
>
> Average referencing reduces the rank of the data by 1. When you
> rereference to average,  the sum of all your channels is 0 at each time
> point.  One channel is therefore a linear combination of the others, which
> implies statistical dependence, therefore the dimensionality of your data
> is reduced  by one after averaging. I always average reference after ICA.
>
> Average referencing before means you can only extract N-1 independent
> components after this.  This is fine as long as you remember to extract 1
> component less than you would have before average reference.
>
> Best wishes,
>
> Jumana
>
>
>
>
>
> *From:* eeglablist-bounces at sccn.ucsd.edu [mailto:eeglablist-bounces@
> sccn.ucsd.edu <eeglablist-bounces at sccn.ucsd.edu>] *On Behalf Of *Eric HG
> *Sent:* 08 December 2016 00:39
> *To:* eeglablist <eeglablist at sccn.ucsd.edu>
> *Subject:* [Eeglablist] Artifacts after removal of ICA component
>
>
>
> Hi everybody,
>
>
>
> I've had some trouble with removal of components using ICA (I'm currently
> using ICA infomax). After I remove a component there seems to be induced
> high frequency noise in the dataset.
>
>
>
> The data is referenced to average before applying ICA.
>
>
>
> Does anyone know why that is happening?
>
>
>
> Best,
>
>
>
> Eric
>
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