[Eeglablist] Signal/noise loss, re-referencing Biosemi data
Jim Kroger
jkroger at nmsu.edu
Mon May 9 11:34:18 PDT 2005
Recently, the following was posted by Arno, and I'm looking for more
details. I've searched the archives thinking there was an earlier, longer
post on this, but can't find it. I have 2 questions about it below:
--------
Finally, do not forget to re-reference your data (otherwise there is a
40dB loss in signal/noise).
--------
1. Biosemi is collected and stored raw, as I understand it, and referencing
is done in software; when I use EMSE I select "common average
reference." Is a similar operation what is meant by re-referencing? I
gather from vague recollection of the previous post that Arno meant the
data must be referenced with a single electrode as the reference.....that
is, the common average reference scheme should NOT be used, or the S/N loss
will occur. Is this correct? If so, since we did not use a reference
electrode for some collected data, which electrode is recommended as the
reference electrode? We are looking at visual attention and working memory,
so occipital, frontal, and parietal are important.
2. Then, should we be collecting data with a reference electrode? Any
reason to do with nose, earlobes, mastoids? Linked?
Thanks
Jim
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