Filtering Problem

[ra_lums]

Hi,

I am new to BCI and I don't have any clear ideas about the filtering in BCI2000. I am performing the P300 speller session. I followed the step by step tutorial on the wiki page of BCI2000. I was able to achieve somewhat good efficiency of 75% sometimes but most of the times its less than 50%.
The problem is I don't have any idea how these "Spatial filter", "P3 Temporal Filter" and "Linear classifier" are helpful in performing the experiment. Kindly someone provide me with the good reference material form where I can study these things.
I am using EMOTIV EPOC headset and the main problem is that it doesn't have electrodes on the center positions. The place where i can observe good P300 response is at locations P7 and O1. Now what I want to do is the software must give high priority to these two channels as compared to rest while performing the online analysis. Someone please tell me how to do this?

Looking forward for your response. Thanks in advance. Any sort of help would be appreciated.

Regards,
Habib

[mellinger]

Hi,

the P300 tutorial mentions the P300Classifier program as an option to automatically determine a configuration that is optimal for a given data set.

A tutorial on how to use P300Classifier may be found at
http://www.bci2000.org/wiki/index.php/U ... r#Tutorial

Regards,
Juergen

[ra_lums]

Hi,

the P300 tutorial mentions the P300Classifier program as an option to automatically determine a configuration that is optimal for a given data set.

A tutorial on how to use P300Classifier may be found at
http://www.bci2000.org/wiki/index.php/U ... r#Tutorial

Regards,
Juergen

I have followed the exact procedure mentioned in the tutorial and that of P300 classifier. The problem is P300 classifier only changes the filtering parameters. I don't just want to perform the experiment I want to know what actually is happening. I just requested to provide me with some links to reference material so that I can figure out the working.
Another thing as I am using Emotiv EPOC headset the tutorial on P300 on BCI wiki page says to change the value of "TransmitChlist"under the storage tab to the values that you have put under "list of channel names" after you have modified the classifier matrix. Initially its value was 1. What is reason of this and why we don't initially change its value?

[mellinger]

I just requested to provide me with some links to reference material so that I can figure out the working.

It's difficult for me to understand which kind of reference you are asking for.

* For reference regarding individual configuration parameters, you may use the "help" button in the Operator module's or BCI2000FileInfo's parameter dialog, and then click a parameter's name. This will open the appropriate reference page in the BCI2000 online help, which is a snapshot of the BCI2000 wiki as it was current when your binary distribution was packaged, and which corresponds to the latest binary distribution when you compiled BCI2000 from source.

* For reference regarding an individual BCI2000 filter, use the above method, clicking on any of the filter's parameters, and scroll to the reference page's top, or search for the filter's name in the BCI2000 wiki.

* For reference regarding the concepts behind the operation of BCI2000 components such as the P300Classifier, perform a google search like this:
http://www.google.com/?q=site:bci2000.o ... Classifier
* For reference regarding general concepts of signal processing or classification, the results of these web searches might be useful:
Spatial filtering of EEG (traditionally called "montage"): http://www.google.com/?q=site:wikipedia.org+eeg+montage
Linear classifier: http://www.google.com/?q=site:wikipedia ... ssifier%22
Stepwise LDA (SWLDA): http://www.google.com/?q=matlab+stepwise

Now what I want to do is the software must give high priority to these two channels as compared to rest while performing the online analysis. Someone please tell me how to do this?

This is done automatically by the parameters which are created by P300Classifier. To exclude other channels from P300Classifier's search, provide only these two channels in P300Classifier's "details->channel list" parameter. To manually select channels and time points, proceed as described in the P300 Tutorial's section about using the "Offline Analysis" tool.

Regards,
Juergen