[Eeglablist] re referencing to average after ICA

[Makoto Miyakoshi]

Dear Raquel,

Just a follow up--

> how do such artifacts impact on time frequency analyses and/or ERP's?

This filter is to help ICA. If you apply time-frequency analysis down to 3
Hz, 1 Hz activity should not affect much (it's not zero, but probably
negligible).

There are several papers saying 1-Hz high-pass 'distorts' ERP and no good.
This is because a traditional averaged ERP waveform is a quite broad band
toward low frequency. You said you know how to copy an ICA weight matrix
calculated on filtered data and copy it to unfiltered data, so you should
be compatible with the conventional ERP practice.

Makoto



On Thu, Sep 1, 2016 at 6:35 AM, Raquel London <raquellondon at gmail.com>
wrote:

> Dear all,
>
> Thank you all for your answers and useful links. I have a follow-up
> question regarding the 1Hz filter Makoto suggests using before running ICA.
> I would use this filter just for the ICA and then apply the weights to the
> unfiltered data. But I was actually wondering about the slow drifts that
> this filter tackles; how do such artifacts impact on time frequency
> analyses and/or ERP's? Can I leave them in (as I would if doing the
> backtransform), provided I am mainly interested in frequencies above 3 Hz?
> Or should I reject these trials regardless?
>
> Thank you!
> Raquel
>
> On Tue, Aug 30, 2016 at 11:08 PM, Akshay Maggu <akshaymaggu86 at gmail.com>
> wrote:
>
>> Hi Raquel,
>> It is usually recommended to clean up all your data, broadly, i.e. remove
>> bad channels, remove large artifacts, HP filter, put to common average
>> *before* you run ICA, for good results. You might wanna refer to
>> Makoto's prep pipeline: https://sccn.ucsd.ed
>> u/wiki/Makoto's_preprocessing_pipeline
>>
>> Bests,
>> Akshay
>>
>> On Tue, Aug 30, 2016 at 11:38 PM, Raquel London <raquellondon at gmail.com>
>> wrote:
>>
>>> Dear eeglabbers,
>>>
>>> I'm using an average reference for my experiment, and I want to try and
>>> use ICA to clean up some dirty electrodes to avoid having to throw them out.
>>> Is it OK to do this first (run ICA, throw out any electrodes that could
>>> not be cleaned with ICA) and then afterwards do the rereferencing to the
>>> average?
>>>
>>> Thank you!
>>> Raquel
>>>
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>>
>>
>>
>> --
>> Akshay Raj Maggu,
>> Laboratory for Language, Learning and the Brain,
>> Department of Linguistics and Modern Languages,
>> The Chinese University of Hong Kong,
>> Hong Kong.
>> Webpage: http://www.cuhk.edu.hk/lin/new/people/students/maggu/
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>> need to.....*
>>
>
>
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-- 
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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