Overview

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:

Connection

The following diagram illustrates how the wiring is done:

You will need the (included) “Audio Pass-Through Cable” to connect StimTracker to the speakers.

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.

ERRATA

Unfortunately, a design error was discovered after StimTracker shipped: the right and left channel are swapped. When StimTracker detects input on the left channel, it will incorrectly flash the “R” LED instead of the “L” one, and vice versa.

For EEG and recording devices that accept 8 bits of input, this does not affect anything because StimTracker generates an event marker when it detects input on either channel. The only devices that are affected are the ones that accept 16 bits of input, namely BioSemi and Brain Products’ USB2.

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Last Revision: May 1, 2020