[Eeglablist] cz/cpz reference

[Clement Lee]

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
> _______________________________________________
> Eeglablist page: http://sccn.ucsd.edu/eeglab/eeglabmail.html
> To unsubscribe, send an empty email to
> eeglablist-unsubscribe at sccn.ucsd.edu
> For digest mode, send an email with the subject "set digest mime" to
> eeglablist-request at sccn.ucsd.edu
>