CheckStimulusBeforeTesting - Meg Wiki

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Check stimuli & system before testing

Always check your stimuli & system before testing. Remember, this is the researcher's responsibility to make sure the stimuli are correct, working and sending the right triggers at the right time.

Find time before your study to discuss your stimulation needs with one of the operators. The best times for pretesting your stimuli and making project settings is when the machine is not used, e.g. during the Helium refill (currently Wednesday mornings). Once everything is ready, make sure you know your project settings, stimulus parameters and trigger box connections. Check these every time before running the actual recordings.


Reset the triggers at the end of the program

In correcting some of the data from the trigger box short, we came upon a couple of instances of E-Prime coding, which can under several circumstances cause problems for data processing. In order to help both your own data processing and your fellow MEG users, please send a "0" trigger at the very beginning and very end of your e-prime script. This will prevent any problems from subsequent user's (and your own previous) scripts affecting your own data and from you affecting other user's data.

E-prime - suggested inline code to add at beginning of Session Procedure:

WritePort &H378, 0

Trigger test

As an additional safety precaution, Maarten van Casteren has written an e-prime script, called "trigger_test", and put it on the desktop of the stimulus pc. The script performs two functions: one is to test all of the triggers. When you run the script, watch the trigger box and make sure you see all of the lights light up and turn off. This will perform two functions: allow you to check the trigger connections are all working, and reset the triggers to 0 so your data will not be affected.

Check the timing

You should always test the timing of your specific script. In addition, it is recommended that you consult an E-Prime expert (of which several qualified people exist at the CBU) with your script and have it checked. Maarten van Casteren has kindly agreed to help you with your E-Prime scripts.

You should make sure you understand exactly what stimulus presentation systems we have and what their limitations are (see StimulusDetails).