ask for some questions about BCI experiment

Known Issues and Problems with BCI2000
Posts: 16
Joined: 04 Jan 2011, 09:44

ask for some questions about BCI experiment

Post by jane1985 » 17 Jan 2011, 12:34

Dear all,
I am a beginner in BCI. my amplifier is g.usbamp. I do the experiments following the" Mu Rhythm BCI Tutoria".
a) Set F3 F4 T7 C3 Cz C4 T8 Pz as channel signals, but I don't know the reference and ground. Does this experiment need the reference and ground? I set the left ear and right ear as reference and ground respectively in the first experiment. but R square is very high at about 50Hz. then I don't set any reference and ground in the second experiment, it seems a little better. What's the value of R square is ok?
b) the band pass is 0.1~60Hz, and the notch is 58~62Hz. when I try to change the band pass and nothch value, then click setconfig, it appears error. So could the bandpass and notch value be changed? how to change?
c) in the Configuring Online Feedback, assume that I get C4 and 12HZ in the offlineline analysis. how to configure Spatial Filter matrix andClassifier Matrix? I don't know the principle.
Need your help. thanks!

Posts: 109
Joined: 28 Feb 2005, 16:31

Post by jawilson » 17 Jan 2011, 22:40

1. Typically, you will use an ear clip for a reference, and a frontal electrode for the ground, such as FPz. This depends on your particular cap or montage. I would try using this for ground, instead of the ear. Do you use a cap, or collodion?

2. The r^2 values should be between about 0.1-0.2 the first time you try the experiment, although higher is usually better, as long as it makes sense. For example, you should expect to see high r^2 values in the mu and beta ranges, but not much higher than 30 Hz in EEG. If you have high 50 Hz values, this is probably indicative of a bad ground/reference (which sounds like it might be the case), since this is the same frequency as electrical line noise in Europe. Fixing the ground/ref should help reduce the 50 Hz component.

3. The error is because the usbamp only accepts certain configurations. See ... _Line_Tool for info on the acceptable settings.

4. For the spatial filter, you want to setup a laplacian filter, which subtracts the surrounding 4 channels from C4. See the Spatial Filter section in ... e_Feedback, which explains it pretty clearly.

Let us know if you still have problems.


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