[Eeglablist] cz/cpz reference

[Kavanaugh, Brian]

Hi Clement,

Thanks for your help. This is great. Correct, Cz is a series of zeros. here
is the prior post I found :
https://sccn.ucsd.edu/pipermail/eeglablist/2016/011153.html

The full rank approach sounds great. But silly question, how does it
identify the reference? I don't see how to specify, especially as this
differs between my two samples (reference in montage for one sample and
reference not in montage in another).

Thanks again Clement,

Brian

On Tue, Mar 10, 2020 at 3:40 PM Clement Lee <cll008 at eng.ucsd.edu> wrote:

> Hi Brian,
>
> Would you link the archived posts from 2016?
>
> Full rank average referencing seems to make most sense here. See
> https://sccn.ucsd.edu/wiki/Makoto's_preprocessing_pipeline#Re-reference_the_data_to_average_.2807.2F18.2F2019_Updated.29
> In your Cpz-referenced datasets, if you were to plot the signal
> acquired from Cpz, it would simply be a channel of zeroes.
> In your Cz-referenced dataset, Cz appears in the EEGLAB montage. Does Cz
> contain a series of zeros? It should, because that's what referencing to a
> single channel is -- subtraction.
>
> It's counterintuitive that setting Cz as a reference before average
> referencing should produce different results than average referencing right
> away. Why should referencing be non-reversible? Removing a channel and
> interpolating afterwards for referencing purposes (and not noise rejection
> purposes) seems wrong too.
>
> Best,
> Clement Lee
> Applications Programmer
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, UC San Diego
> 858-822-7535
>
>
> On Tue, Mar 10, 2020 at 11:16 AM Kavanaugh, Brian <
> brian_kavanaugh at brown.edu> wrote:
>
>> Hi everyone,
>>
>> I have a question about cz/cpz reference.
>>
>> We collected eeg in two separate samples. in one sample, cpz was the
>> reference (and we re-referenced to average after). in the other sample,
>> cpz
>> wasn't working, so cz was switched to the reference. bc cz was originally
>> set as a recording electrode and because it does appear in eeglab
>> montage, I set cz as reference in eeglab and then re-referenced to
>> average,
>> similar to eeglab wiki recommendations.
>>
>> is this the correct approach? i saw a thread from 2016 that said to remove
>> cz, re-reference to average, and then interpolate cz, but wasn't sure if
>> this is still best approach.
>>
>> after low pass filter, i used cleanline and clean_rawdata. before running
>> ica, i wanted to compare the two samples. oddly, the samples have the
>> opposite association between gamma power and test performance (r = -.3
>> vs. + .3). Does this make any sense to anyone?
>>
>> Thanks for your help!
>>
>> brian
>>
>> --
>> Brian Kavanaugh, PsyD.
>> Pediatric Neuropsychologist, E. P. Bradley Hospital/Rhode Island Hospital
>> Assistant Professor (Research), Warren Alpert Medical School of Brown
>> University
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-- 
Brian Kavanaugh, PsyD.
Pediatric Neuropsychologist, E. P. Bradley Hospital/Rhode Island Hospital
Assistant Professor (Research), Warren Alpert Medical School of Brown
University