High level of delta in the samples

[coada_florin]

Hello everyone,

My name is Florin and I am currently working on a project using g.MOBIlab+ with g.LadyBird (Ag/Cl active sensors). I am trying to conduct a comparison between the activity of the brain during different games in different environments. The software used to record data is BCI2000 and the tools used to analyse is eeglab.

When I looked at the data I saw large level of delta waves. Has anyone seen something similar before?
Link to graphs with data:
s16.postimg.org/uv9flrqdx/image.jpg

Regards,
Florin

Edit: A few more details on this.
The tests were conducted on a number of 21 volunteers, each sample gathered showed the same large amount of Delta.
As I am sure we all know the Delta Wave (High Amplitude – Low Frequency) in an electroencephalogram is directly connected with: a) special states of the Brains (Sleep…etc.) b) some serious malfunctions (Wolff-Parkinson-White Syndrome, sleep deprivation…etc.) and, c) with some bad habits (Alcoholism...etc.). As a result, is probably the only band of frequencies we can fairly surely expect not to possess a dominant signature in the spectrums recorded under the activities investigated.

Is there some sort of parameter in BCI2000 that I can set wrong to get unwanted frequencies?
Is there some kind of noise, which poorly filtered causes this? If so what would be the cause of such noise?

[gschalk]

Hi,

I am not sure where you see delta waves. The spectra seem perfectly normal, i.e., 1/f drop-off with a peak in the alpha range. Also, there is no parameter to influence the spectrum of the signal, as the data file is an exact replica of what comes from the amplifier.

Gerv

[coada_florin]

Hi Gerv,

Thanks for the help. Still, I am a bit confused, what do you mean by "1/f drop-off"? I thought the beginning of the chart (values<4) shows Delta values, and (4-8 Theta).

More charts here:
docs.google.com/file/d/0B2xVIptXwI2sUXl6S0Z0UGlUR2c/edit

Florin

[gschalk]

Hi,

Check out

http://www.bci2000.org/wiki/index.php/U ... _Mu_Rhythm

The spectra there look very similar to the spectra you are showing.

For 1/f, check out

http://www.ploscompbiol.org/article/inf ... bi.1000609

I hope this helps.
Gerv

[coada_florin]

Hi Gerv,

Thanks for the links. They're helping me to better understand the situation and what is going on.
So if I were to make some assumptions on this chart-> s16.postimg.org/uv9flrqdx/image.jpg

Would it be correct to assume that the alpha levels in the second column reflect the relaxed/reflecting state of the users?
Or should I mention that this might also have something to do with the mu activity of the brain, because it falls approximately under the same frequencies?

Sorry about all the questions, I'm a bit new to the area and the papers that I'm reading don't always clarify things for me.

Regards,
Florin