'P3 protocol'

[lorencea]

Hello,

I'm writing an application that uses the P3 signal processor, but I'm not totally sure how I can get the two to work together. From what I've read, the two communicate through changing different states and proper times? Any help or walkthrough you can give would be wonderful.

Thanks!
Tony

[gschalk]

Hi,

Please check out

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

Basically, when StimulusRes goes to a non-zero number x, the first control signal that the Application receives will contain the classification result for stimulus x. Thus, just watch StimulusRes and then collect classification results. When configured properly, the stimulus with the highest classification result will contain the P300.

Gerv

[lorencea]

Hey thanks for the help!

I got the states all figured out now. My next question is what should I do with the classification results? I have 7 of them (one for each row and column in my 3 by 4 arrangement), each with it's own 1 by 2 matrix. but I'm not really sure what to do with them...

Any further help is much appreciated
Thanks
Tony

[gschalk]

At least if configured properly, the classification results give a metric how much a particular stimulus elicited a P300. In other words, look for the largest number (perhaps separately for all rows and columns - I do not know what your display looks like). The selected stimulus is the one with the largest number.

Gerv

[lorencea]

Ok, that sounds simple. One last question, my classification results for each stimulus are in a vector form with two numbers (e.g. [x, y]). So, which of the two do I take? Or do I take the length of the vector?

By the way, my display is very similar to the BCI2000 P3Speller, but with images instead of letters.

[gschalk]

I believe the classification result is in the first control signal.

Gerv