Strange waveform shown in EEGLab


#1

Hello everyone!

I’m trying to analyse my channel data from a recorded .csv (MuseMonitor-Android). I only recorded all 4 channels in constant mode. When i try to load it into EEGLab (V14.1.2) it shows the 4 channels in the channel data (scroll) but the i cannot see the amplitudes. (Please see the attached pic)

Can anyone tell me why it looks like this? what am i missing? i followed the instructions of the EEGLab Youtube channel… won’t work.

Thanks in advace!


#2

I’ve not used EEGLab, or seen the video (can you post a link?) … but I can see an amplitude in your screenshot, right at the bottom: where it says: “AF7 Time; 0.4, Value: 200.56”. Also the lines in the graph at not flat, they’re moving… so this looks like it’s working to me. You probably just have to set you min/max values for the display better. i.e. zoom in a bit :slight_smile:


#3

Thanks for your fast reply! :slight_smile:
you can find the videos here:
https://www.youtube.com/channel/UCK8x1bdiHWmT0yCNEjTcEvA

yes, thats whats confusing to me. The lines are moving but this was only a short test-record and should look like a beta brainwave… so even if you only see 0.4s there should be at least 6-7 amplitudes or am i mistaken? where do i set up the min/max values? in the musemonitor app?

Thanks again!!


#4

Try changing the box in the bottom right that says 1000, to something more like 100.


#5

Does not look much better :confused:

is it maybe the recorded file? are there any settings which could cause these values?


#6

It’s working, but you’ll need to use a 256Hz file if you want more data points. This look 1Hz to me.


#7

Yes yes yes, that was it. when i load the file in eeglab, it automaticly chooses the a 1hz sample-rate. when i put in 256hz it looks like this:

Thanks so much for your help! :pray:

I hope you don’t mind another question… i get a little confused when i look at those waves… it looks like a gamma frequency with about 39hz but i guess that is not correct. can i even determine that frequency my brain is working on with this data?


#8

This is the raw data, so you’d need to do an FFT to find out what the power spectral density for each frequency is. What you’re looking at here are the raw voltages.
I’m pretty sure I saw the guy do and FFT breakdown in one of the videos, but like I said, I’ve never used this software, so I’m not sure how you do it.

The recording data already contains pre-computed values for all the major brainwaves. You’d only need to do an FFT if you want to break it down further to smaller frequency ranges. If you just want to look at your Gamma power, then you can load the CSV into the online viewer at https://MuseMonitor.com/Chart.php and it’ll show you right away.


#9

It looks like i was mistaken with my understanding off brainwaves. I thought the brain is working in one frequency wich changes in order to change the state.
So what your saying is that every frequency is present at any time but the power (or spectral density) of a certain frequency determines what state the brain is in?

If i look on the Brainwaves through your online viewer i see a couple of delta peaks in the first minutes.
But this probably does not mean that my brain was working in delta!?

Would you have an idea of where i can learn how to read brainwave freqs? i don’t want to bother you forever :wink:

Thanks again!


#10

Correct, all frequencies happen all the time. When people say they are for example “in Alpha” this means that Alpha is the dominant wave at that point in time.

The wikipedia article on Alpha waves is a great place to start learning, from there, there are many links to other articles.

So far as identifying relaxation goes, a good read is the research paper “My Virtual Dream: Collective Neurofeedback in an Immersive Art Environment” by Natasha Kovacevic, Petra Ritter, William Tays, Sylvain Moreno, Anthony Randal McIntosh: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0130129