[Eeglablist] imported BrainVision data: finding the reference electrode

[Ricardo Moura]

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
>>>>
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>>>
>>>
>>>
>>> --
>>> 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/
>
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