Theta/beta ratio

[Guest guest]

Buck,

There is a direct linear conversion (don't recall the number exactly any more, something like P-to-P being 1.7 or 2.7 times RMS). May be that p-to-p is easier and faster to calculate. Perhaps Lenny, Ian or other digital signal processing folk can help with this.

Pete

I'm just getting started into all of this, but my interest if for my son with ADD. I've read Demos book Getting Started with Neurofeedback. It seems bizare to me to use " power " measurements which are a squaring of a peak to peak signal. Are there any studies which have compared peak, to square of peak, to RMS values of the same data? I'm not sure why RMS is not used. Maybe it's a moot point in that with EEG signals you get the same general information independent of which you look at. But for arbitrary signals, it can make a huge difference.

O Van Deusen wrote:

Jim,

The s are using a (simplified) version of the work of Monastra and Lubar (I was a co-author of the first study in Neuropsychology in the mid-90's), which attempted to define for various age groups the " cutoff point " for ADHD using the T/B ratio. We all measured at Cz, using an A620 amplifier and power ratios. We all used 4-8 for Theta and 13-21 hz for beta.

The data that resulted and were published actually ranged from a top of around 3.0 for children around 5 to below 2.0 for young adults. The problem that I had with this publication--which I found out years later from another of the participants he too had reported--was that it assumed only an upper cutoff point. Many of us then--even before I had much contact with the Othmers--were seeing that inattentive type ADD usually showed HIGH ratios, BUT...hyperactive/impulsive type ADHD often showed LOW ratios, lower than the " normal " range. For reasons of their own, the primary authors chose not to complicate the system further with this information.

Children's brains speed up from birth into the low-to-mid 20's as the axons are covered with myelin sheaths, which allow signals to be transmitted more rapidly. Hence there is a consistent shift (in a normally-developing brain) toward beta and away from theta frequencies in waking states. As a result, the theta/beta ratio changes toward lower numbers throughout that period.

The TLC, as we have discussed previously here, is NOT a normative assessment, it is a descriptive assessment. I've seen kids with power ratios in the middle 2's who had real attention problems and others close to 4 who did not. You have to add delta and alpha into the equation. If the world were as simple as just looking at the T/B ratio, we'd all be happier, I guess. So the TLC values ( " expected " , not " normal " ) are for adults. The trainer's job is to look at those values in light of the client's age, to note how they are different in various parts of the brain, to note how they change (or don't) when the client goes from eyes-closed to eyes-open to Task states, to see whether they are stronger on the left or right, etc. Those help us describe how the brain is activating. Looking at those data through the window of the client's desired training objectives, we can get an idea of how to train.

I hope this helps.

Pete

On 4/10/07, Jimmy Ekgren <j-ekgren@...

> wrote:

Pete, You mentioned that theta sq/beta sq ratio should be within 1.2-2.0. I can't figure how that should work. To me it seems more reasonable that theta/beta (without squares) should be within 1.2-2.0. s theta/beta ratio is 4-8/16-20. According to indication of ADHD is 4-8/16-20 > 2.5 for children. And greater than 2.0 for adults. Measured at Cz or Fz. When using a 4-8/13-21 ratio (no squares), the ratios will allways be less than the s ratio. Which will fit in with the TLC 1.2 - 2.0. However when using 4-8 sq/13-21 sq, you will get a much higher ratio. Jim

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http://www.brain-trainer.com305/433-3160The Learning Curve, Inc.

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pvdtlc@...http://www.brain-trainer.com305/433-3160The Learning Curve, Inc.

[Guest guest]

Hi all,

I have for some time been interested in EEG signal analysis. For those

interested in learning more

about signal analysis there a pdf file located at the site which can be

useful:

http://cp.literature.agilent.com/litweb/pdf/5952-8898E.pdf

In fact I have developed a method which can analyse EEG in real time just by

using the

peak-to-trough and the time between the peak-to-peak of two waves. This

gives you the

amplitude and the frequency for each wave and thus you can get a wave by

wave EEG

analysis. You can have a look at the summary at the site:

http://cienciacognitiva.planetaclix.pt/MPhil.html

the whole thing at:

http://cienciacognitiva.planetaclix.pt/MPhil.zip

Bye for now,

-------

Prof.Dr. Alvoeiro, PhD(Hull,UK) C.Psychol(BPS,UK)

2000-119 Santarém

Portugal

eMail: labreabcog@...