While the onset of an auditory stimulus can be marked by having the stimulus presentation computer send event markers, timing will be more accurate and setup would be simpler if one took advantage of StimTracker's built-in audio marking capability. Instead of connecting the computer to external speakers like this:
You can route the signal via StimTracker:
The following diagram illustrates how the wiring is done:
You will need an extra cable to connect StimTracker to the speakers (it's included).
When wired this way, StimTracker monitors the auditory level and sends an event marker to the EEG recorder when the volume rises above a preset threshold. See Using StimTracker for information on setting the threshold. The auditory signal is not altered. StimTracker monitors the auditory level for each of the right and left channels independently.