Re: Help with TLC assessment

[Guest guest]

Glyn,

Try expanding the range of the Power Spectrum to 50 Hz (right-click on each side

separately and choose Properties). If you really have 50 Hz interference, you

should see a very tall spike right at 50. EMG (muscle) artifact also causes

activity in the 50 Hz range, though it is not likely to be as concentrated right

at 50 Hz. Normally we would expect that a true electromagnetic (EMF) signal

would not come and go like you describe, while muscle activity could. Sometimes

it's easier to see in the Power Spectrum display than anywhere else.

The effect of EMF or EMG activity would generally be to increase levels of

faster frequencies, especially in the high-beta range and to increase fast-wave

coherence levels (since the signals are coming from a common source, just not

one in the brain.) If you have either of these, obviously it will cause a

mis-statement of what is truly there.

If you are having trouble keeping hair out of the way, try putting a dab of

paste on your middle finger tip and using index finger and thumb to clear the

hair, then dab the paste on the skin. That should keep the hair off the site,

and you can place the Activ electrode. Because the Activ's clean up impedances

before sending the signal, it is unlikely that this would cause what you are

seeing, though it could result in a weaker signal.

It sounds like you have something corrupted in your file as well. Beta peak

frequencies are calculated in a range from 15-38 Hz, so they cannot, be

definition, be below 15. Alpha Peak Frequencies could be 10-11; in fact that's

probably where they should be for an adult.

Pete

>

> From: " glyn68 " <glyn@...>

> Date: 2006/03/05 Sun PM 05:29:13 EST

>

> Subject: Help with TLC assessment

>

> Firstly, I am seeing apparent EM interference. The 50 Hz meter (in the

TLC assessment design for BE) shows quite high %'s. (I am in Europe so

50Hz is the mains frequency.) I see anything from 1% to 90%, and

though sometimes it is low I can't figure out when it's low and when high.

My first question is, does it matter? Is it going to stuff up the

assessment, or parts of it? If so which parts are not reliable?

My second question is, is there anything I'm doing wrong?

I'm using the ActivEEG electrodes with my J & J C2+.

As I'm practising on myself, I struggle to get my hair out of the way

- could that be part of the problem?

The second problem is that my beta peak frequencies are consistently

showing up as 10-11 Hz - I can't figure that one out at all...