[Eeglablist] reference channel information (from net station raw data)

[Makoto Miyakoshi]

Dear Jerry,

Most likely the referenced 'Cz' is not stored as data but computed on the
fly as a mean of the other 128ch.

The 'recovered' reference channel is completely dependent of others and
does not add any information; it can even confuses ICA with rank mismatch
(i.e. number of channels ~= data rand). So it is generally not recommended
in EEGLAB.

Maktoo

On Mon, Jun 16, 2014 at 3:31 PM, Jerry Zhu <jerryzhu at siu.edu> wrote:

> Hi all,
> I used net station to export my 128-channel data as .raw format with and
> without exporting reference channel (which is Cz in my case). That is, I
> had two .raw files.
>
> Then when I opened them in eeglab, it did not recognize the reference
> channel as Cz (automatically) for both files. Both files showed they had
> 128 channels. I expect that the file with the reference channel would show
> it has 129 channel (with Cz).
>
> Next, my head model has location information about Cz, so I declared Cz as
> my reference channel (through GUI "set reference"). The eeglab main window
> showed that the reference was set to Cz. But when I plotted the data, the
> figure did not show Cz. Again I expect the channel number would increase to
> 129 and the plot would show a flat line indication Cz is the reference
> channel.
>
> Finally, I could add Cz to the data by re-referencing to average (through
> GUI re-reference | add current reference channel back to data)
>
> Can someone explain this to me?
> Thank you so much for the help!
>
> Best,
> Jerry
> --
> Jian Zhu, M.A.
> Brain and Cognitive Sciences
> Department of Psychology
> Southern Illinois University Carbondale
> Web: http://zhupsy.com
>
> We have two halves in the brain: left and right. Nothing is right in the
> left. Nothing is left in the right.
>
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-- 
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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