Directly sent selected target to P3 speller

Forum for discussion on different user applications
Locked
PeterLiu
Posts: 9
Joined: 20 Oct 2011, 21:46

Directly sent selected target to P3 speller

Post by PeterLiu » 11 Nov 2011, 23:09

Hi all,

I wonder if there is a way to sent the selected target to P3 speller directly instead of sending stimulusCodeRes and Classification score (signal processing module is fieldtrip buffer, matlab). We want to implement our own decision making part. Also, I need the P3 speller to stop and begin next trial immediately after received the selected target for realizing a dynamic stop strategy. Thank you very much.

Yichuan

mellinger
Posts: 1210
Joined: 12 Feb 2003, 11:06

Re: Directly sent selected target to P3 speller

Post by mellinger » 15 Nov 2011, 12:12

Hi Yichuan,

this is not possible with an unmodified version of the P3Speller. Also, it does not make too much sense IMHO because signal processing code only sees StimulusCodes, which are associated with _groups_ of targets (rows and columns) rather than targets themselves. Only the P3Speller knows how targets relate to StimulusCodes, so your signal processing code cannot determine the selected target.

However, you can encode a selection by transmitting a pseudo classification score which is 1 for each row or column which contains the desired target, and which is 0 for each row or column that does not contain the desired target.
Also, I need the P3 speller to stop and begin next trial immediately after received the selected target for realizing a dynamic stop strategy.
For a dynamic stop strategy, you will need to modify the P3Speller source code. To end a sequence, it must return two 0s in sequence from its OnNextStimulusCode() function.

Regards,
Juergen

nokhbe
Posts: 3
Joined: 08 Dec 2012, 07:28

Re: Directly sent selected target to P3 speller

Post by nokhbe » 16 Feb 2013, 18:44

Dear Jeurgen,

Thanks for your response to the previous person. I am stuck in the same situation. I want to do the classification in my fieldtrip signal processing.
Can you indicate me how to "encode a selection by transmitting a pseudo classification score which is 1 for each row or column which contains the desired target, and which is 0 for each row or column that does not contain the desired target" ?

Thanks for your time,
Alireza

mellinger
Posts: 1210
Joined: 12 Feb 2003, 11:06

Re: Directly sent selected target to P3 speller

Post by mellinger » 25 Feb 2013, 10:24

Hi Alireza,

there is a parallel thread which discusses how to send likelihood values to the P300 speller through the FieldTripBuffer:
http://www.bci2000.org/phpbb/viewtopic.php?f=4&t=1281

Let me know if you need additional information.

Regards,
Juergen

Locked

Who is online

Users browsing this forum: No registered users and 29 guests