Thank you very much for your attention. It's a bit embarressing but to be frank I was mainly worried it signified I'd done something wrong in running the participant, or something of the like, and was artifactual in nature. Naive of me of course, I appreciate your input.<br>
<br>As long as it's not artifactual it shouldn't be a problem for what I want with these data.<br><br>-M<br><br><br><div class="gmail_quote">On Mon, Feb 27, 2012 at 5:15 PM, <span dir="ltr"><<a href="mailto:tognoli@ccs.fau.edu">tognoli@ccs.fau.edu</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Dear Matthew,<br>
<br>
>From the figures that you sent, it seems to me that you deal with two<br>
noticeable sets of rhythmic activities:<br>
-The channels placed on the upper part of the figure carry some typical<br>
alpha frequency. You have a good view onto them from time marker 520.5 to<br>
522 and again later at time marker 524. If you count the interval between<br>
two peaks, you should see (for this subject) a ~10-11Hz. The topography<br>
would tell you which of several 10Hz activities you are dealing with, e.g.<br>
alpha, mu or others.<br>
<br>
-There is also another activity that is prominent across a broad range of<br>
channels at time markers 522-523, much slower in the theta range (roughly<br>
~6Hz). More information on its spatial distribution would be necessary to<br>
draw some hypotheses about its significance.<br>
<br>
With kind regards,<br>
______________________________________________<br>
<br>
Emmanuelle Tognoli - PhD<br>
<a href="http://www.ccs.fau.edu/%7Etognoli" target="_blank">http://www.ccs.fau.edu/~tognoli</a><br>
Center for Complex Systems and Brain Sciences<br>
Florida Atlantic University<br>
<div><div class="h5"><br>
> Thanks Steve/Tarik/Andrew,<br>
><br>
> Of course it's alpha! I knew it would be something stupid and elementary<br>
> like that. My EEG education so far has been very narrow, basically I've<br>
> just been learning everything I need to know to troubleshoot this study as<br>
> issues arise.<br>
><br>
> I should have known given how incredibly mind numbingly boring my study<br>
> is.<br>
><br>
> Thanks again.<br>
><br>
> -Matthew<br>
><br>
><br>
><br>
> On Mon, Feb 27, 2012 at 2:56 PM, Stephen Politzer-Ahles <<br>
> <a href="mailto:politzerahless@gmail.com">politzerahless@gmail.com</a>> wrote:<br>
><br>
>> Hi Matthew,<br>
>><br>
>> To me this looks a bit like alpha waves (common when a subject is<br>
>> getting<br>
>> tired, shutting their eyes, about to doze off, etc.) but I can't really<br>
>> be<br>
>> sure. I can't read the channel labels in your images, but alpha waves<br>
>> tend<br>
>> to show up the most robustly on posterior channels, so that would be one<br>
>> way to tell if that's what they are. If it is alpha waves, there are<br>
>> different opinions out there about what to do with them. Some<br>
>> experimenters<br>
>> usually reject stretches with alpha waves, whereas others believe they<br>
>> can<br>
>> often be left in if they're not too big (I believe Steve Luck's (2005)<br>
>> book<br>
>> has more information about this in the chapter on artifact rejection; I<br>
>> don't have a copy handy right now so I don't remember exactly what it<br>
>> says). In our lab we never try to remove them by filtering, because they<br>
>> tend to be in more or less the same frequency range as the<br>
>> (language-related) cognitive activity we're interested in; I'm not sure<br>
>> what frequency ranges you're interested in so I'm not sure if filtering<br>
>> would be appropriate or not. In my experience, alpha waves of about this<br>
>> size have seemed to get more or less averaged out of the ERPs if there<br>
>> are<br>
>> enough trials, but others on the list may be able to give more feedback.<br>
>><br>
>> Good luck,<br>
>> Steve Politzer-Ahles<br>
>><br>
>> On Mon, Feb 27, 2012 at 7:56 AM, Matthew Stief <<a href="mailto:ms2272@cornell.edu">ms2272@cornell.edu</a>><br>
>> wrote:<br>
>><br>
>>> Hi Everyone,<br>
>>><br>
>>> I was wondering if anyone has had any experience with the "wavy"<br>
>>> activity that seems to go across almost all of the channels in this<br>
>>> subjects data. I am sure it is familiar to you but I have not seen it<br>
>>> in<br>
>>> any of the text books or guides I can find online and don't have an<br>
>>> experienced person supervising me.<br>
>>><br>
>>> Here's what the strange activity looks like in filtered, cleaned,<br>
>>> epoched, and baselined data...<br>
>>><br>
>>><br>
>>> <a href="http://s1153.photobucket.com/albums/p512/mstief/?action=view¤t=wavychannels7.jpg" target="_blank">http://s1153.photobucket.com/albums/p512/mstief/?action=view¤t=wavychannels7.jpg</a><br>
>>><br>
>>><br>
>>> Going back to the same dataset before any processing has been done, you<br>
>>> can see the same waves. Obviously this is not particularly clean data,<br>
>>> but<br>
>>> is it salvageable?<br>
>>><br>
>>><br>
>>> <a href="http://s1153.photobucket.com/albums/p512/mstief/?action=view¤t=wavychannels8.jpg" target="_blank">http://s1153.photobucket.com/albums/p512/mstief/?action=view¤t=wavychannels8.jpg</a><br>
>>><br>
>>><br>
>>> Here's the exact same stretch of data after it has gone through 1hz<br>
>>> high<br>
>>> pass and 55hz low pass filters.<br>
>>><br>
>>><br>
>>> <a href="http://s1153.photobucket.com/albums/p512/mstief/?action=view¤t=wavychannels10.jpg" target="_blank">http://s1153.photobucket.com/albums/p512/mstief/?action=view¤t=wavychannels10.jpg</a><br>
>>><br>
>>><br>
>>> It does seem to be affecting the ERPs at least to my untutored eye,<br>
>>> here's one channel.<br>
>>><br>
>>><br>
>>> <a href="http://s1153.photobucket.com/albums/p512/mstief/?action=view¤t=wavychannels4.jpg" target="_blank">http://s1153.photobucket.com/albums/p512/mstief/?action=view¤t=wavychannels4.jpg</a><br>
>>><br>
>>><br>
>>> So what is it? Normal? Horrible? Fatal or merely deleterious? Given<br>
>>> that it seems to contaminate most or all of the data for this person<br>
>>> should<br>
>>> I just throw it out or can I get something out of it? In particular<br>
>>> how<br>
>>> will ICA handle it? Do I still have a chance of getting a stable<br>
>>> decomposition out of it with a reliably identifiable P1? This person<br>
>>> was<br>
>>> particularly bad but there are less drastic examples in several of my<br>
>>> other<br>
>>> participants. Keep in mind some of my participants are rather rare and<br>
>>> would be difficult to replace (I study sexual orientation and some<br>
>>> varieties are less common than others).<br>
>>><br>
>>> --<br>
>>> _________________________________________________________________<br>
>>> Matthew Stief<br>
>>> Human Development | Sex & Gender Lab | Cornell University<br>
>>> <a href="http://www.human.cornell.edu/HD/sexgender" target="_blank">http://www.human.cornell.edu/HD/sexgender</a><br>
>>><br>
>>><br>
>>> Heterosexuality isn't normal, it's just common.<br>
>>> -Dorothy Parker<br>
>>><br>
>>> _______________________________________________<br>
>>> Eeglablist page: <a href="http://sccn.ucsd.edu/eeglab/eeglabmail.html" target="_blank">http://sccn.ucsd.edu/eeglab/eeglabmail.html</a><br>
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>>><br>
>><br>
>><br>
>><br>
>> --<br>
>> Stephen Politzer-Ahles<br>
>> University of Kansas<br>
>> Linguistics Department<br>
>> <a href="http://www.linguistics.ku.edu/" target="_blank">http://www.linguistics.ku.edu/</a><br>
>><br>
><br>
><br>
><br>
> --<br>
> _________________________________________________________________<br>
> Matthew Stief<br>
> Human Development | Sex & Gender Lab | Cornell University<br>
> <a href="http://www.human.cornell.edu/HD/sexgender" target="_blank">http://www.human.cornell.edu/HD/sexgender</a><br>
><br>
><br>
> Heterosexuality isn't normal, it's just common.<br>
> -Dorothy Parker<br>
><br>
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</blockquote></div><br><br clear="all"><br>-- <br>_________________________________________________________________<br>Matthew Stief<br>Human Development | Sex & Gender Lab | Cornell University<br><a href="http://www.human.cornell.edu/HD/sexgender" target="_blank">http://www.human.cornell.edu/HD/sexgender</a><br>
<br><br>Heterosexuality isn't normal, it's just common.<br>-Dorothy Parker<br>