Checking your triggers

There are a few things you need to insure once you have figured out which triggers you will use for your stimuli.

First, insure that the mapping is correct i.e. that you have effectively associated the triggers you wish with the stimulus/event you wish in your stimulus delivery software. Do triple-check it!

Second, get a sense of whether all things are being sent correcly by letting the ACQ software "go!" and looking at the trigger lines.

Third, you want to know what are the possible delays between the time you send your trigger to the ACQ software (via the PC stim) and what the subject actually does in real life (i.e. see, hear, make a response etc). For this, you can make an empty room measurement, record the trigger lines, and measure the timing of your stimuli (with a photocell and a microphone) directly placed in the MEG room. Carefully follow the procedure detailed here: measuring stimulus-trigger delays

Fourth, double-check once more once you have recorded your first pilot that everything is ok, timed ok, coding ok etc...!