[Eeglablist] Re-reference after ICA cleaning for BioSemi data

[Tarik S Bel-Bahar]

Hello Ben,

I've referenced before ICA with biosemi data,
as well as only rereferencing after the ICA. I think both are near
equivalent as long as you control for the rank in how you PCA the ICA. On
the list I've seen suggestions for both pre-ICA and for post-ICA
rereferencing.

Just rereference after the ICA.

Also make sure you are using only good channels for your rereferencing,
whenever you do it.

Note that you probably have some issue with whole head coverage so average
reference is not recommended.

It cannot hurt to run ICA and rereferencing several different ways, and
review the results for yourself. I don't think enough people take the time
to do that.

I think once you've ICAed, you can remove components safely, and then stay
in channel-level data.

I don't think any referencing of the ICA matrices themselves is necessary,
though I may be wrong, please let us know if you find out otherwise.








On Thu, Jan 7, 2016 at 4:04 PM, Benjamin Skerritt-Davis <bsd at jhu.edu> wrote:

> Hi everyone,
>
> I need some advice on cleaning BioSemi EEG data using ICA. I have data
> with 38 channels, and I would like to be able to analyze the data using
> different re-reference channels after ICA cleaning (e.g., linked mastoids,
> nose). My intuition is to run ICA on all 38 channels (before
> re-referencing) so the data is full rank, project out any "bad" components,
> then re-reference the cleaned data.  A couple of questions:
>
> 1) Given that BioSemi data is collected essentially "reference-free", is
> it OK to perform ICA before re-referencing?
>
> 2) After using ICA to remove eye blink components and project back to
> sensor space, can I re-reference the cleaned data directly?  Or do I need
> to first re-reference the original data AND the unmixing matrix from the
> ICA before removing the bad components?
>
>
> I've found conflicting answers to similar questions online, so I'm hoping
> for consensus this time around. =)
>
> Thanks for the help,
> -Ben
>
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