[Eeglablist] re-referencing

[Sarnthein Johannes]

Dear Nikolai,

we do exactly the same thing you want to do.
These are the lines that you need for your script
(I don't remember the GUI-buttons to be clicked):

% re-references 61 cephalic channels to (M1+M2)/2: chans 40 and 60; 
% excludes bipolar channels 62:64 from re-referencing
EEG.data = reref(EEG.data, [40 60], 'method', 'withref', 'refloc',{
'CPz',180,0.1},...
'exclude', [62:64],'keepref', 'off');
% assigns new electrode labels and coordinates
EEG.chanlocs=pop_chanedit(EEG.chanlocs, 'load',{ 'fms63.loc',
'filetype',''});

The file fms63.loc contains the new electrode listing.
Be aware that the data from CPz now appear at EEG.data(end,:).
This means that you have to label your last EEG trace with CPz 
and assign the according coordinates in fms63.loc.
(I had tried for some days to get the trace of CPz between CP1 and CP2
but finally gave up).

Best,
Johannes


________________________________

Von: eeglablist-bounces at sccn.ucsd.edu
[mailto:eeglablist-bounces at sccn.ucsd.edu] Im Auftrag von Nikolai
Novitski
Gesendet: Dienstag, 8. Mai 2007 22:23
An: eeglablist at sccn.ucsd.edu
Betreff: [Eeglablist] re-referencing


Dear all,
 
We are recording EEG in Neuroscan referenced to CPz; the position of the
reference it is hard-wired in our Maglink cap. Then we need to
rereference to the average of both mastoid leads. It goes ok if no ICA
had performed on this data. After the ICA however the program returns an
error on trying to re-reference to the average of 2 electrodes.
Re-referencing to one single electrode it works ok. It wouldn't be a
problem to re-reference before ICA, but we also have two bipolar
channels for EOG and those are treated as referenced to common reference
during rereferencing, thus they are re-referenced together with all the
rest. 
So, I have two questions.
 
1) Is there any reason why re-refencing to more than one electrode
doesn't work after or is it a bug?
 
2)Is it possible to mark bipolar channels as bipolar so that they are
not effected by the re-referencing of the common-referenced electrodes?
 
Thank you in advance.
 
Nikolai Novitski,
KU Leuven