[Eeglablist] Options for bad reference (mastoid) channels

[Becky Prince]

Dear EEGLAB list,

I've run an ERP study on auditory temporal expectations in which I'm
interested in the auditory N2b and P3b components.  I believe the
convention is to use the average of linked ears or mastoids as the
reference for optimal measurement of these components, but my mastoid
channels are consistently noisy in all of my participants.  The mastoid
channels have higher impedances (~15 KOhms) than the other sites, probably
due to the fact that the caps we use have built in mastoid sites that don't
fit close enough to the skin.

I'm guessing it's a bad idea to re-reference to noisy channels, so I'm
wondering what my options are.  Can anyone explain what they would do in
this situation?  Are there any resources that explain the effects of
re-referencing on specific components?  I'm wondering if I'll be able to
see changes in N2b/P3b if I use another reference, e.g. average of all
electrodes, and how the appearance of the components (sites/polarities)
will be different from those typically reported with a linked ear or
mastoid reference.

Apologies for the fact that this isn't strictly an EEGLAB question - I'm
hoping someone will still offer some advice!

Thanks,
Becky
____________________________________________

Becky Gilbert (nee Prince)
PhD Researcher

Room A109
Department of Psychology
University of York
Heslington, York, YO10 5DD, UK
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://sccn.ucsd.edu/pipermail/eeglablist/attachments/20130918/dfada76c/attachment.html>