[Eeglablist] imported BrainVision data: finding the reference electrode

[Stephen Politzer-Ahles]

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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