Transient Responses

"In general, transient responses are evoked by stimuli that occur infrequently (in theory, only once), and steady-state responses are evoked by stimuli that occur more rapidly." Picton (2002)

There is a wide variety of transient neurophysiological measures. Within the auditory field these are commonly delineated by their latency and anatomical source location. Fast (2-20 ms) responses are often described as auditory brainstem response. Middle (10-100 ms) are commonly termed middle latency responses or midbrain evoked potentials. And slow cortical responses (50-300 ms) are commonly called P1-N1-P2 complexes. There is also late responses (150-1000 ms) which are also cortical in nature and include mismatched negativity responses, P300, N400, P600 responses.

I assume things are similar for other cognitive fields, but given how us researchers don't talk outside our circles, they probably have different naming.