From: peterson_at_d...
Date: 2001-09-05 02:34:46
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.
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. 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. 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.
Also, traditionally, alpha-theta is usually trained at O1, which is
on the back of the head. 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
effect.
--- In buildcheapeeg_at_yahoogroups.com, "Joerg Hansmann" <info_at_jhansmann.de> wrote:
> Hi,
>
> since about 5 days I am using the comEEG prototype for
> Alpha/Theta audio-feedback. Electrode positions for
> 1 channel are Cz - A2
> (A2 should be right ear lobe. Is that right ? My picture with
electrode-
> positions is a little bit unclear).
>
> Audio-feedback is given using two sine-wave oscillators (one lower
> frequency for Theta and one higher frequency to indicate Alpha)
> which amplitudes are controlled by the geometric addition
> (root sum of squares) of the FFT output for each frequency band.
>
> If a (fixed) threshold of 25uV is met, the feedback sound
> is played at a low volume. A voltage between 25uV and 50uV increases
> the volume and everything above 50uV is played at maximum volume.
>
> With this setup I have been able to increase Alpha (lying position,
eyes
> closed), so that the Alpha-feedback sound is played nearly 100% of
time.
>
> However I have no idea how to get significant Theta.
>
> What am I doing wrong ?
> Should I train Alpha with higher thresholds first ?
>
> And what is the great difference in
> inner perception between Alpha and Theta ?
>
>
> Regards,
>
> Joerg
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