[Eeglablist] Artifact Rejection

[Edward Justin Modestino, M.Phil.]

Hello,
In the EEGLAB tutorial on artifact rejection, it mentions the default trim
percentage is 5%.  Are there any references for using this default of 5%? 
Or is this based on general statistics of a 95% confidence, or something
similar?

If I were to perform a amplitude thresholding on a channel by channel
basis, what amplitude in +/- microvolts would be considered an upper
limit?   Should this be dynamic and thus be a different microvolt +/-
amplitude value cutoff for each channel? Are there any reference papers
for this?

I have one reference Picton et al. (2000), an article about guidelines for
ERPs which includes recording standards and publication criteria.  In this
article on page 138, it mentions that a criterion level of +/- 200
microvolts could be used to remove trials.  It mentions this may be too
Conservative for sleep studies which may have higher amplitudes.  This +/-
200 microvolts sounds far too liberal to me.  I believe the eye movements
I have already removed from the data were much less than that!  I think a
more conservative estimate might be reasonable.  The default for EEGLAB is
+/- 25 microvolts.  Is there a reference paper for this?  Is this based on
statistics of previous data?

Is it unreasonable to see +/- 30 microvolts, or up to +/- 40 microvolts in
single trials?  I get the feeling that +/- 200 microvolts(Picton et al.,
2000) is too liberal and perhaps +/- 25 microvolts (EEGLAB default) may be
too conservative for my data.

If anyone has any reasonable answers to my questions, I would appreciate it.
Thank you,
Ed Modestino
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Edward Justin Modestino, M.Phil.
Graduate Research Assistant
Cognitive Neurophysiology Laboratory
Center for Complex Systems and Brain Sciences
Ph.D. Program in Complex Systems and Brain Sciences
Florida Atlantic University
(561) 297-2238
Fax: (561) 297-3634
modestino at ccs.fau.edu
http://www.ccs.fau.edu/~modestino/
Lab: http://www.ccs.fau.edu/~bressler/CNL/CNL.html
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