[Eeglablist] imported BrainVision data: finding the reference electrode

[Stephen Politzer-Ahles]

Hi Ricardo,

That's strange, it does indeed sound like it referenced to just that
channel. I'll have to go back and double-check how I did my data at the
time.

It's definitely possible to reference the data in Analyzer and then import
it. After referencing the data in Analyzer, you can use the Generic Data
Export tool there to export the header, marker, and eeg files in .dat
format, and then use pop_loadbv() in EEGLAB to import them.

Best,
Steve

On Mon, Sep 24, 2012 at 10:09 PM, Ricardo Moura <ricardoojm at gmail.com>wrote:

> Hi Steve,
>
> I have just done what you said, and when I plot the data, the signal in
> the right mastoid electrode is turned to a flat line. It seems that all of
> the data was re-referenced only to this channel. If I try "add current
> reference channel to the data", I get the error message again (there are no
> reference channels)...
>
> Do you know if there is a way to export the data already re-referenced
> from the BrainVision analyzer? Now I am trying the analysis using the raw
> data.
>
> Thank you very much once again.
>
> Best,
> Ricardo
>
> On 24 September 2012 23:59, Stephen Politzer-Ahles <
> politzerahless at gmail.com> wrote:
>
>> Hi Ricardo,
>>
>> If I'm understanding correctly, you should be able to get the average
>> mastoid by choosing right mastoid as your reference and selecting "retain
>> old reference channels". This should average together the right mastoid
>> with the current reference (the left mastoid) and compute a new reference
>> based on that average.
>>
>> Best,
>> Steve
>>
>>
>> On Mon, Sep 24, 2012 at 9:39 PM, Ricardo Moura <ricardoojm at gmail.com>wrote:
>>
>>> Hi,
>>> Thanks for your answer.
>>> The reference channels were recorded at the left (recording reference)
>>> and right (recorded as a normal eeg channel) mastoids. The right reference
>>> is available when I open the data in EEG lab, but not the recording
>>> reference. The reference channel always appear as "unknown" at the main
>>> eeglab window, and when I go to the "channel locations", it only shows me
>>> 64 electrodes (the 65th electrode, which would be the recording reference,
>>> is missing). This is a problem because I need this channel in order to
>>> re-reference the data to linked-ears (don't I?). But I don't need to use it
>>> as an active electrode.
>>>
>>> So when I try the  "Add current reference channel back into the data" ,
>>> I allways have the following message: "there are no reference channel
>>> defined, add it using the channel locations".
>>>
>>>
>>> Any idea about how to recover this channel (in case I really need it to
>>> perform the linked-ears reference)?
>>>
>>> Best,
>>> Ricardo
>>>
>>>
>>> On 24 September 2012 14:50, Stephen Politzer-Ahles <
>>> politzerahless at gmail.com> wrote:
>>>
>>>> Hi Ricardo,
>>>>
>>>> May I ask what your reference was? In my experience using Brain Vision
>>>> data, the recording reference (in my case it was on the nose) was just not
>>>> included in the data that I imported to EEGLAB. This wasn't a problem for
>>>> me because I wasn't interested in analyzing that electrode anyway after I
>>>> re-referenced; but it might matter for you if your reference is something
>>>> that you care about as an active electrode, like Cz. You may be able to get
>>>> that channel back by using the "Add current reference channel back into the
>>>> data" command and specifying its location (but I haven't tried that myself
>>>> with BV).
>>>>
>>>> Best,
>>>> Steve
>>>>
>>>> On Mon, Sep 24, 2012 at 8:55 AM, Ricardo Moura <ricardoojm at gmail.com>wrote:
>>>>
>>>>> Dear all,
>>>>>
>>>>> I am new to the EEGLab. Now I am trying to analyze data that were
>>>>> recorded using the BrainVision recorder, but I never find the reference
>>>>> electrode. Going to "Channel Locations" only shows me the EEG electrodes.
>>>>> It is a problem for me because I want to re-reference the eeg signal to the
>>>>> linked-ears. The second reference electrode is always there (once it was
>>>>> recorded as a regular eeg electrode), but not the actual reference.
>>>>>
>>>>> I would appreciate any help,
>>>>> Best,
>>>>> Ricardo Moura
>>>>>
>>>>> _______________________________________________
>>>>> 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
>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> Stephen Politzer-Ahles
>>>> University of Kansas
>>>> Linguistics Department
>>>> http://people.ku.edu/~sjpa/
>>>>
>>>
>>>
>>
>>
>> --
>> Stephen Politzer-Ahles
>> University of Kansas
>> Linguistics Department
>> http://people.ku.edu/~sjpa/
>>
>
>


-- 
Stephen Politzer-Ahles
University of Kansas
Linguistics Department
http://people.ku.edu/~sjpa/
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://sccn.ucsd.edu/pipermail/eeglablist/attachments/20120924/35fc21bd/attachment.html>