The NeXus Trigger Interface (NTI) is an add-on to the NeXus family with a digital input (NeXus-10 and NeXus-32). The NTI is used to monitor stimuli/events (sound, light, digital) and synchronizes these with the physiological signal that NeXus is acquiring.

One of the major areas that the NTI can be used in is event related potentials (ERP) and evoked potentials (EP) (For more information see: http://www.mindmedia.nl/english/pdf/biotrace-nexus-erp-ep-functions.pdf

Take a look at the NeXus Trigger Interface Webpage