[Eeglablist] Rereference using interpolated electrode

[Makoto Miyakoshi]

Dear Tamar,

If the interpolation you used is completely linear e.g. something like
Cz_interpolated = (Fz + Pz)/2, there is no problem. It is just like
re-referncing to mathematically linked earlobes or mastoids which is a
common practice (which does not mean it is particularly reasonable, by the
way.)

If the interpolation algorithm uses spline etc, the error that occurs there
will affect your re-referenced data.

Conclusion: choose a simple linear interpolation and re-referencing to that
electrode is ok.

Makoto

On Sat, Oct 17, 2020 at 3:33 PM Tamar Cohen <ctamar76 at gmail.com> wrote:

> Hi all,
>
> I'm migrating a model with a certain reference to a system missing the
> original reference electrode (using ultra sparse cap- less than 5
> electrodes).
> I tried to interpolate the original reference electrode (which is between
> two electrodes we record) and received good accuracy for several recordings
> (higher than when using a different reference. Tested against the original
> reference).
>
> Assuming an ultra sparse setting- I'm aware that average reference is not
> recommended for such setups, but using an interpolated reference does seem
> to perform better than when changing to a different reference.
> How problematic it is to interpolate the reference in such a sparse
> setting?
>
> Many thanks
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