The mismatch negativity response (MMN) is an event-related potential that is believed
to reflect the automatic (possibly preconscious) neural processing of changes in ongoing
environmental sounds. The MMN involves a negative voltage shift of baseline electroencephalographic
(EEG) activity in the approximate latency window of the N1 and P2 cortical potentials
in response to new or novel sounds. The most commonly used laboratory tests for extracting
the MMN from EEG activity all involve oddball stimulus presentation procedures in
which the interstimulus intervals (ISIs) of the frequently occurring standard sounds
are shorter in length then that of the infrequently occurring deviant sounds. This
presents the possibility that the MMN response could be affected by neuronal refractory
or recovery events. The present study tested 12 young females, using the syllabic
events /da/ and /ga/ as standard and deviant stimuli, and found evidence that, with
certain experimental protocols, ISI-dependent neural refractory effects can affect
the morphology of the MMN, possibly resulting in misinterpretation of the underlying
neural bases of the response.
Key Words
Auditory event-related potentials - auditory evoked potentials - mismatch negativity
- speech
