[Eeglablist] Artifact Rejection

Edward Justin Modestino, M.Phil. modestino at ccs.fau.edu
Mon Jul 25 09:18:06 PDT 2005

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

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
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
Lab: http://www.ccs.fau.edu/~bressler/CNL/CNL.html
"Any intelligent fool can make things bigger, more complex, and more
violent. It takes a touch of genius--and a lot of courage--to move in the
opposite direction."   E. F. Schumacker

"Great spirits have always found violent opposition from mediocrities. The
latter cannot understand it when a man does not thoughtlessly submit to
hereditary prejudices but honestly and courageously uses his
intelligence."  Albert Einstein

More information about the eeglablist mailing list