[Eeglablist] Importing BIOSEMI Data and Re-referencing to the Robust Average using PREP

[Matthew Stief]

Hello,

I have a question regarding the robust referencing approach of PREP and how
it relates to the importation of BIOSEMI data that asks for an reference
electrode when it is being imported.  For my data we used mastoid
electrodes anticipating that these would be used as the reference on
importation.

EEGLAB provides a warning that failing to indicate a reference on
importation will add noise to the data.  Am I correct in understanding
that, regardless of this warning, if BIOSEMI is imported without indicating
a reference and then put through the PREP pipeline, that subtracting out
the robust average reference will negate this issue of noise?  That is what
I think is correct but I would like wiser heads to confirm it.

Second, I have already imported all of my data using the mastoid electrodes
as the reference.  If I understand correctly, if I apply the PREP pipeline
to this imported and mastoid-referenced data, even after re-referencing to
the robust average, I would still be vulnerable to contamination from a
noisy mastoid electrode, as that noise would have been added to all of the
data.  Or would re-referencing to the average successfully negate that
problem?  It would be convenient if I didn't have to start from scratch
with the unimported data as the channel locations for each subject (109 of
them) have been set up and they vary slightly by cap size so it would be
some labor to make sure that that was all set up again correctly in the new
pipeline of the raw unimported data.

_________________________________________________________________
Matthew Stief
Human Development | Sex & Gender Lab | Cornell University
http://www.human.cornell.edu/hd/sexgender

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