question

[Guest guest]

anybody out there who has Weimers for their child's teacher?

[Guest guest]

,

Yes, these things are correct:

1. An EEG amplifier is a differential amplifier, so it shows us the difference between the active and reference electrode.

2. A monopolar montage uses a reference over a relatively inert EEG site (like the earlobe), so the value it subtracts is close to zero, and it is unlikely to change as a result of training. Therefore, any changes we see in a monopolar training are likely to happen at the active electrode site.

3. A bipolar montage uses a reference electrode over a brain site, so we are comparing two active EEG signals. Either or both sites may change as a result of training. It is not possible to tell what changed or where in a bipolar montage--only that, as you say, either the signals got more alike (inhibit) or more different (reward).

4. In a bipolar montage you don't have any way to know which site is higher or lower, you can't tell if the change that took place during training was the the low side changed, the high side changed, they both changed or there was some change in their phase relationship, which would affect coherence.

5. Although Siegfried Othmer is fond of arguing that bipolar montages (which the Othmers use almost exclusively) are a " poor man's coherence " training, I'm not aware of anything actually demonstrating that is true. Of course if two signals are out of phase by 180 degrees (peak of one wave is lined up with the trough of the second), then the difference between the two will be as large as it can be, and the sum will be very small. For example, if alpha at one site is +10uV and at the other site is -10uV, subtracting +10 - -10 will give a differnce of 20. Adding a +10 and a -10 will give a difference of 0. On the other hand, if the two waves are perfectly in phase (peaks and troughs are lined up), the sum will be very large (+10 + 10=20 uV) and the difference will be very small (-10 - -10=0). So IF two signals happen to be out of phase, then bipolar training could lead them to change their phase relationship. Of course, with bipolar montages you have no way of knowing if they are coherent or in phase or not, since you need two channels to measure that. But what if they are already in phase when you begin training to reduce in a bipolar montage? They can't get MORE in phase, yet you will likely still be able to train down the difference. So obviously other things CAN change with a bipolar montage.

6. Coherence does not measure how alike two frequencies are. Two signals that are consistently 180 degrees out of phase will be exactly as coherent as two signals that are consistently perfectly IN phase! Coherence is simply a measure of the stability of the phase relationship between the two waves. Coherence doesn't measure the amplitude relationship between the two waves either. One could be a huge signal, and the other a very small signal, but as long as their peaks and troughs are happening in some kind of consistent relationship, they can be coherent.

I hope this doesn't just confuse things more.

Pete

2008/2/22 R. :

I'm trying to figure it out how the bipolar training really works. Let me explain myself. If a unipolar or monopolar montage is the differential amplitude between the active electrode and the reference, let's say, measuring alpha =10 uv, when we train this specific frequency we are inviting the brain to increase or decrease this amplitude, no?! Well, if this statement is correct, a bipolar montage is the differential between the activity beneath the active electrode and the reference electrode, so if we see a 10uv we may assume that is the difference between the alpha amplitude at the left side minus the alpha amplitude of the right side. And this may apply for all frequencies, so if this is correct, when we are training up or down any of these frequencies, we are really training the difference between the left and right frequencies, so when we are inhibiting e.g. Theta we are closing the gap or difference between these two sites (e.g. T3/T4), but when we are rewarding, we are crating a bigger gap or difference between each other. So at the end, the bipolar montage should work like coherence training, in the sense that we are opening or closing the difference between certain frequencies.

-- Van Deusenpvdtlc@...http://www.brain-trainer.com

305/433-3160The Learning Curve, Inc.