1189Re: [buildcheapeeg] Re: Alpha/Theta feedback
- Sep 10, 2001Hi,
----- Original Message -----
Sent: Wednesday, September 05, 2001 3:34 AM
Subject: [buildcheapeeg] Re: Alpha/Theta feedback
> Joerg--Glad to hear you are playing with alpha-theta. Yes. A2
> (actually Au2) would be the right earlobe. If your other electrode
> is at Cz I imagine you could use your left earlobe (Au1) instead if
> you wanted to, with no particular difference in effect.
That would be interesting to verify with a 2 channel device.
I have heard that often Au1 and Au2 are tied together.
> Many people--I suppose most--are able to produce stronger alpha than
> theta. You should set the theta threshold separately, not use the
> same one as for alpha.
I have now implemented this feature in the comEEG SW.
> You will need to experiment to get the right
> threshold, but it should be one that provides feedback about 25% of
> the time for theta.
How is this threshold adjustment done in professional NFB SW ?
At the moment I can only imagine 2 ways to do this:
1) manual threshold adjustment by trial and error.
2) automatic adjustment at program start: For a defined period (a few minutes)
the SW samples EEG-data and calculates the threshold to meet the 25%
> Also as you get better at producing either alpha
> or theta, you can set the threshold for that band up higher. If
> you're exceeding an alpha threshold of 25 uV 90% of the time, set it
> up a few microvolts til you're only exceeding threshold 50 or 60% of
> the time.
I will do this.
With the fixed thresholds my NFB-experiments are getting boring and ineffective.
> Also, traditionally, alpha-theta is usually trained at O1, which is
> on the back of the head.
I could imagine that in lying position O1 is susceptible for
artifacts caused by varying pressure (head on cushion) on
> Both the Greens and Peniston use(d) this
> site. Find a bony bump at the back of your head about 3 or 4 cm from
> the top of your neck. This bump is called the inion, and is a
> beginning-point for locating EEG sites. O1 will be about 2.5 cm up
> and 2.5 cm to the left of that bony protrusion.
> Actually, though, since you started training at Cz, there is probably
> no reason to change now. At least one published alpha-theta study
> used (if I remember correctly) C3 and got perfectly good results, so
> probably anywhere from Cz back is OK.
> If you just want to train alpha, Pz is probably the best site, but
> again Cz would be OK. Since you apparently aren't getting much
> feedback on theta, you are probably actually doing alpha training in
I do not know, how much Theta I would get with correctly adjusted thresholds.
Therefore the next thing I will implement is some session statistics.
This seems very important to me for tracking progress and to
find the right adjustment for the feedback thresholds.
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