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

[Jerry Zhu]

Hi Makoto,
Thank you for your reply.

While playing with my two .raw files, I did notice that eeglab deleted the
empty reference channel which did exist in one of my .raw file but not the
other (I chose to include reference channel in only one file).

It says: Delete empty data reference channel (reference channel location is
retained). But I noticed that eeglab only mark that channel type as REF.
The reference on the main window still shows unknown.

This seems to explain my phenomenon.

I may have another question about computing average reference, which I
think it might be better to open another thread.

Thank you!
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.


On Mon, Jun 16, 2014 at 6:32 PM, Makoto Miyakoshi <mmiyakoshi at ucsd.edu>
wrote:

> 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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