User Tutorial:Performing a P300 Spelling Session
This step assumes that you created a subject-specific configuration file for the on-line speller, as described in the previous step of this tutorial.
Preparation
If you quit BCI2000 after the previous step, start it using the appropriate batch file at batch/P3Speller_<YourAmplifier>.bat, or the link to that file which you created on the desktop.
Then, load the configuration file that you saved in the previous step.
Click Set Config to view the EEG signal, and prepare the subject for EEG recording as you did for the initial session.
Instructions to the Subject
On the subject's screen, a speller matrix is presented as already familiar from the initial session. Differently from that session, there is no text suggested; rather, the subject may choose freely which letters, words, and sentences to write.
- You will see a speller matrix, containing letters, numbers, and punctuation marks.
- To write a certain letter, concentrate on it, e.g. by counting the number of flashes that occur for it.
- After some time, a result will be classified and appended to the text field located at the top of the window.
- If the letter that appeared is not what you intended, concentrate on the "backspace" or "undo" field to remove it.
Additional instructions should be given regarding minimization of artifacts from
- Contraction of the muscles of the face/head, swallowing;
- Eye blinks and eye movements;
- Motion.
Provided that subjects are asked to minimize artifacts (e.g. asked to try to swallow only during the pause between letters), he/she should be further assisted in these efforts by providing a comfortable chair and a dimly lit room. We will return to the role of reinforcement, but it is already clear that the experimenter must carefully monitor the EEG and alert the subject in the case he/she has forgotten some of the instructions. When the experimenter is sure that his/her instructions have been well understood, the recording session may start.
Click the Start button to start the spelling experiment.
Multiple Sessions
Once a run has ended, BCI2000 goes into suspended state. Further runs will be added to the session when you click Resume.
When starting the next session, don't forget to increment the SessionNumber parameter on the Storage tab. Otherwise, new runs will be added to the previous session's directory. As a safety net, BCI2000 will never overwrite existing data files, and documents date and time in the StorageTime parameter. This allows to later separate data files into runs even if the SessionNumber parameter has not been increased.
Finished
Here, the P300 speller tutorial is finished.
Congratulations! You are now able to perform P300 spelling experiments.