[Eeglablist] Oddly "Wavy" Data

[Matthew Stief]

Hi Everyone,

I was wondering if anyone has had any experience with the "wavy" activity
that seems to go across almost all of the channels in this subjects data.
I am sure it is familiar to you but I have not seen it in any of the text
books or guides I can find online and don't have an experienced person
supervising me.

Here's what the strange activity looks like in filtered, cleaned, epoched,
and baselined data...

http://s1153.photobucket.com/albums/p512/mstief/?action=view&current=wavychannels7.jpg


Going back to the same dataset before any processing has been done, you can
see the same waves.  Obviously this is not particularly clean data, but is
it salvageable?

http://s1153.photobucket.com/albums/p512/mstief/?action=view&current=wavychannels8.jpg


Here's the exact same stretch of data after it has gone through 1hz high
pass and 55hz low pass filters.

http://s1153.photobucket.com/albums/p512/mstief/?action=view&current=wavychannels10.jpg


It does seem to be affecting the ERPs at least to my untutored eye, here's
one channel.

http://s1153.photobucket.com/albums/p512/mstief/?action=view&current=wavychannels4.jpg


So what is it?  Normal?  Horrible?  Fatal or merely deleterious?  Given
that it seems to contaminate most or all of the data for this person should
I just throw it out or can I get something out of it?  In particular how
will ICA handle it?  Do I still have a chance of getting a stable
decomposition out of it with a reliably identifiable P1?  This person was
particularly bad but there are less drastic examples in several of my other
participants.  Keep in mind some of my participants are rather rare and
would be difficult to replace (I study sexual orientation and some
varieties are less common than others).

-- 
_________________________________________________________________
Matthew Stief
Human Development | Sex & Gender Lab | Cornell University
http://www.human.cornell.edu/HD/sexgender


Heterosexuality isn't normal, it's just common.
-Dorothy Parker
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