[Eeglablist] re-reference to average of both earlobes
wildja at ohsu.edu
Fri Jun 13 14:02:12 PDT 2008
Is there a way to use the GUI to create a reference that is a weighted
linear combination of two electrodes (ie, not necessarily the average)?
Heather Jaskirat Wild, Ph.D.
OHSU - Dept of Neurology
Mail Code CR-120
3181 SW Sam Jackson Park Rd
Portland, OR 97239
(office) 503 494 7219 (fax) 503 494 9520
Oregon Center for Complementary and Alternative Medicine in
Neurological Disorders (ORCCAMIND)
>>> "arno delorme" <arno at ucsd.edu> 6/13/2008 2:07 AM >>>
Dear Andre and David,
yes, you may use the GUI to re-reference to two channels. Simply enter
both channel indices when performing re-referencing.
If one of the channel is already the reference and is not present in
the data (as 0), then first compute average reference (enter the
reference channel name and location if any when computing average
reference). You may then rereference to the average of this reference
channel and another one. If you are doubfull, you may test after this
procedure that your data is indeed the same as if you had simply
subtracted half of the second channel from the command line (EEG.data
= EEG.data - EEG.data(ref,:,:)/2).
Note that the advantage of using the GUI is that it also transform the
ICA matrices if any to take into account re-referencing.
> If your data was recorded using one earlobe as a reference, you can
> use the following function:
> It was written for re-referencing data to the average of the mastoid
> electrodes, but it can do the job for you. Where the function
> requests the index of the non-original-reference mastoid electrode
> (i.e., the variable "mastoid_id"), just use the index of the non-
> original-reference earlobe electrode.
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