[Eeglablist] Using ICA with EEG, ECG and EOG.

[Dario Madeo]

Thank you Alois for your tips!

By the way, I'm really interested in using ICA because the work I'm on is
based on
some result provided by someone else using ICA. I can't get rid from ICA at
the moment
but I'll consider to try your suggestion for future works!

On Fri, May 18, 2012 at 8:36 AM, Alois Schloegl <alois.schloegl at ist.ac.at>wrote:

> Hi Dario,
>
>
> if you want to do a fully automated EOG/ECG correction, you can use
> REGRESS_EOG.M from biosig/t250 (I guess it comes with eeglab). In my
> experience, regression will work better than fully automated ICA (for
> details see [1]).
>
> It works this way:
>  [s,HDR]=sload(filename);
>  [M,N]=size(s);
>
>  eocg = sparse(N,3);
>  eocg(#H+,1)=1;        % replace #H with the number of your H++ channel)
>  eocg(#H-,1)=-1; %
>  eocg(#V+,2)=1;
>  eocg(#V-,2)=-1;
>  eocg(#EKG+,3)=1;
>  eocg(#EKG-,3)=-1;
>
> A fully automated identification of these channels is needed to automate
> that step. The function identify_eog_channels() is trying to do this, but
> because of a lack of standardization it's likely it won't work correctly.
> Though, You might want to adapt it to your data.
>
>  eegchan = [... ]; % list of your EEG channels
>  R = regress_eog(s, eegchan, eocg);
>  s_corr = s*R.s0;      % corrected eeg channels
>
>
> A view remarks:
>
> - You can expect the best performance when R = regress_eog(..) is computed
> from a data segment with large EOG and EKG artifacts (ask the subject to
> perform different eye movements at the beginning of the recording).
>
> - ECG has 3 spatial components, but only one is removed. Therefore, you
> can expect only a limited performance on the ECG artifact.
>
> - if the function identify_eog_channels() works properly on your data, the
> method can be fully automated. See also
>   help regress_eog
>   help identify_eog_channels
>   help get_regress_eog
>   help sload
>
>   Alois
>
> [1] http://precedings.nature.com/**documents/3446/version/1/**
> files/npre20093446-1.pdf<http://precedings.nature.com/documents/3446/version/1/files/npre20093446-1.pdf>
>
>
>
>
> On 05/17/2012 05:57 PM, Dario Madeo wrote:
>
>> Hi all,
>>
>> I'm a new user in the fantastic EEGLAB world :) !
>> I have a question about the removal of ECG and EOG artifacts from EEG
>> data.
>>
>> Here is my scenario: I have 40 channels, where:
>> - 34 are EEG of which I know the location on scalp
>> - 4 are EOG (namely H++, H-, V++, V-)
>> - 2 are EKG (namely EKG++, EKG-).
>>
>> I load the dataset, and after this operation I would like to immediately
>> run an ICA decomposition
>> (I need to do something else before this?).
>> But actually I really don't now how to correctly use this dataset with the
>> ICA decomposition.
>> Should I run the ICA only on the 34 eeg channels, or maybe on all 40
>> channels? (in the
>> relative GUI i can decide to do ICA on a certain subset of channels).
>> The aim is to exclude the influence of the ECG/EOG artifacts from EEG data
>> to accomplish further analysis.
>>
>> Can anyone help me?
>>
>> Thanks a lot!
>>
>> D.M.
>>
>>
>>
>>
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>
>


-- 
--- Dario Madeo
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