[Eeglablist] Oddly "Wavy" Data

[ANDREW HILL]

Just looks like Alpha to me.. e.g. normal and not a problem.  

Of course, filtering at 1hz will cause other problems with your ERPs..

Best,

andrew

 

On Today 5:56 AM, ms2272 at cornell.edu wrote: 

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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