[Eeglablist] EOG Artifact removal before ICA?

Marco Buiatti marco.buiatti at gmail.com
Wed Jun 3 23:40:19 PDT 2015


Dear Alexander,

Makoto's pipeline is perfect for applying ADJUST, and I agree with Makoto
that you should not remove blink and eye movement artifacts before doing
ICA, otherwise there will not be clear artifact "examples" that ICA can
identify.

For an alternative preprocessing pipeline, see ADJUST tutorial here:
http://www.unicog.org/pm/uploads/MEG/TutorialADJUST1_1.pdf

Best,

Marco

On 3 June 2015 at 20:14, Makoto Miyakoshi <mmiyakoshi at ucsd.edu> wrote:

> Dear Alexander,
>
> Here is Makoto's pipeline for your info
> http://sccn.ucsd.edu/wiki/Makoto%27s_preprocessing_pipeline
>
> Don't use EOG artifact remover before ICA. Let ICA take care of it, since
> it's the best algorithm to decompose EOG and blinks. I compared 33ch vs.
> same data but reduced to 3ch (Fz, Cz, Pz) and run ICA. Interestingly, the
> first component in both results showed identical ERPimage!
>
> If you apply ICA, apply high-pass filter at 1Hz with transition bandwidth
> 1Hz (0.25-0.75Hz transition).
>
> You may not need to epoch before ICA. Make sure that you have enough (i.e.
> channel^2 x 30 or larger) datapoints if sampled at 250Hz (you can
> downsample to 125Hz if you inspect only up to 60Hz or around... this
> actually helps ICA)
>
> I have no experience with ADJUST, sorry.
>
> If you re-reference, do it to average reference. According to Jason
> Palmer, it's better that you average reference before ICA (but after
> bad-channel removal).
>
> Makoto
>
> On Fri, May 29, 2015 at 5:26 AM, Alexander Quent <alexander.quent at rub.de>
> wrote:
>
>> Hello,
>> I have a more general question concerning the order of steps in
>> pre-processing process.
>>
>> Aim: I want to look at negative mean amplitudes between 440 and 540 msec.
>>
>> My set up:
>> 32 channels of which 4 are used for recording EOG and 1 is used an
>> additional mastoid reference electrode.
>>
>> My general plan:
>> I want to use remove artifacts using ICA. What I am asking myself is
>> whether it is legitimate to remove EOG artifacts before running the ICA
>> using a different plugin? Is the apparent redundancy in any way
>> problematic?
>> This is what I want to do:
>> 1. Removing slow linear trend (high pass filter circa 0.3 Hz)
>> 2. Removing EOG artifacts using BSS with AAR plugin
>> (http://www.germangh.com/eeglab_plugin_aar/)
>> 3. Removing EOG channels
>> 4. Visually inspect data for artifacts
>> 5. Remove bad channels
>> 6. Low pass filter and epoching
>> 7. Run ICA
>> 8. Run ADJUST 1.1
>> 9. Re-reference to linked mastoid and baseline correction
>>
>> Since this is my first ERP analysis, I am sure whether this pipeline is
>> legitimate: Especially due to the fact that I want use BSS and ICA, but
>> also whether it is okay to re-reference to linked mastoid at the end.
>>
>> Maybe you have some advise for me.
>>
>> With best regards,
>> Alexander Quent
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>
>
>
> --
> Makoto Miyakoshi
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego
>
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-- 
Marco Buiatti

Neonatal Neurocognition Lab
Center for Mind/Brain Sciences
University of Trento,
Corso Bettini 31, 38068 Rovereto (TN), Italy
E-mail: marco.buiatti at unitn.it
Phone: +39 0464-808178

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