[Eeglablist] Does EEG.icaact represent components in channel reference?

[Makoto Miyakoshi]

Dear Martin,

> After I run ICA, does the structure EEG.data contains the components
transformed in channel-by-times?

EEG.data is a channel x time structure. EEG.icaact is IC x time structure.
They have the same length. EEG.data remains the same before and after ICA
calculation.

Makoto



On Fri, Feb 10, 2017 at 7:30 AM, Martin Simoneau <
Martin.Simoneau at kin.ulaval.ca> wrote:

> Dear Makoto,
>
>
>
> Thanks for your answer.
>
>
>
> After I run ICA, does the structure EEG.data contains the components
> transformed in channel-by-times?
>
>
>
> If not, how can I transform back the components in channel-by-time series?
>
>
>
> Regards,
>
>
>
> Martin
>
>
>
>
>
> *De :* Makoto Miyakoshi [mailto:mmiyakoshi at ucsd.edu]
> *Envoyé :* jeudi 9 février 2017 22:42
> *À :* Martin Simoneau <Martin.Simoneau at kin.ulaval.ca>
> *Cc :* eeglablist at sccn.ucsd.edu
> *Objet :* Re: [Eeglablist] Does EEG.icaact represent components in
> channel reference?
>
>
>
> Dear Martin,
>
>
>
> > As a result, if row 20 in EEG.data represents C3, analysing row 20 in
> EEG.icaact is analysing C3, am I right?
>
>
>
> No. Channels and ICs are related via weight matrix. It's not one to one!
>
>
>
> > In other words, if I remove components, it is possible that C3 is no
> longer present.
>
>
>
> No. When you remove IC20, then the backprojection of the remaining ICs
> will miss contribution by IC20.
>
>
>
> Makoto
>
>
>
>
>
> On Tue, Feb 7, 2017 at 1:08 PM, Martin Simoneau <
> Martin.Simoneau at kin.ulaval.ca> wrote:
>
> Hi everyone,
>
>
>
> I have questions regarding this sentence: “the components were transformed
> back to the channel-by-time series.” From my understanding, the authors ran
> ICA on their EEG channels. Thereafter, transformed back to the channel
> time-series meant that they used EEG.icaact to analyse their time-series in
> EEG channel reference. Therefore, the time-series in EEG.icaact are the
> components in the channel reference, am I right?
>
>
>
> As a result, if row 20 in EEG.data represents C3, analysing row 20 in
> EEG.icaact is analysing C3, am I right?
>
>
>
> However, if I remove components because some showed eye blink or other
> artefact, now EEG.icaact has less row than EEG.data. How can I find C3
> after removing components?
>
>
>
> In other words, if I remove components, it is possible that C3 is no
> longer present. Can I transform components back in channel-by-time series
> without losing some channels after removing components?
>
>
>
> Thanks for your help,
>
>
>
> Martin
>
>
>
>
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>
>
>
> --
>
> Makoto Miyakoshi
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego
>



-- 
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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