Synchronization EEG with eye-tracking

Question

We are doing an experiment combining EEG and eye-tracking. We write both the 'user field' on the eye-tracking element and the EEG triggers in the after onset snippet of each event (triggers set is Manual). The question I have is whether this is the best snippet for this purpose, or whether it is better to use another one. Basically my concern is having the maximum synchronization between the two techniques.

Answer 1

'After Onset' snippet is the best for sending an EEG trigger, since that snippet is called right after the event onset (when the event is presented on the screen). You should use the runtime command

 SendOutputNow=true; 

of the port element, when it works in the manual mode. Alternatively, you can use a port element in the 'Output on the event onset' mode, and then change the trigger value in the 'Before Onset' snippet. This also makes sending triggers slightly faster (about 1 ms) than in the manual mode.