[Eeglablist] Rereference

[Simon Finnigan]

Hi All

Firstly I must say that as a scientist, I find the rationale from Jason via Makoto to be un-scientific and unsatisfactory.

Second - This will only partly answer your question I think, but here goes: it all depends on how you're analysing your data [what you're looking  at/for] and particularly, whether or not scalp topographies are of interest to you - but in general and in brief, the consensus seems to be that common-average referencing is preferable over mastoid referencing, at least - and probably other references sites too [e.g. vertex; nasion]. [Also are your data referenced to one or both mastoids? and if both - were they linked, or averaged together after recording?]

My 2002 paper in 'Neuropsychologia' addressed this issue scientifically, at least in part - e.g. see final figure [albeit we weren't doing ICA back then either!].

Regards, Simon


On 04/10/2014, at 8:21, Makoto Miyakoshi <mmiyakoshi at ucsd.edu> wrote:

> Here is update.
> I asked the question to Jason. He told me that the main reason avg reference is useful is that it returns brain maps that look like nice localized sources inside the head with red blob and slight negative (aqua/green) background. This makes sense.
> 
> Makoto
> 
> On Thu, Oct 2, 2014 at 10:00 AM, Makoto Miyakoshi <mmiyakoshi at ucsd.edu> wrote:
>> Dear Eric,
>> 
>> I have the same question for long time. In my case, because I run ICA and remain in IC analysis and almost never come back to channels, I really wonder if I need re-referencing at all.
>> 
>> I've heard Jason Palmer, who wrote AMICA for EEGLAB, say average reference before ICA is necessary, but he did not give me a clear explanation for that. Scott wanted to know it too, but we were interrupted at that time. Next time I'll ask it to him (when I ever see him in the lab...)
>> 
>> Makoto 
>> 
>> On Tue, Sep 30, 2014 at 2:44 PM, Eric HG <erichg2013 at gmail.com> wrote:
>>> Dear list,
>>> 
>>> I have read the tutorial on the site and it says: "Converting data, before analysis, from fixed or common reference (for example, from a common earlobe or other channel reference) to 'average reference' is advocated by some researchers, particularly when the electrode montage covers nearly the whole head (as for some high-density recording systems)." 
>>> 
>>> I have data collected with a mastoid reference and I was wondering in which cases it would be considered best to rereference to the average? Are there any specific papers about rereferencing that anyone would recommend?
>>> 
>>> Regards,
>>> 
>>> Eric 
>>> 
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>> 
>> 
>> 
>> -- 
>> Makoto Miyakoshi
>> Swartz Center for Computational Neuroscience
>> Institute for Neural Computation, University of California San Diego
> 
> 
> 
> -- 
> Makoto Miyakoshi
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego
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