In hearing, a deviant sound can differ from the standards in one or more perceptual features such as pitch, duration, loudness, or location.
[3] During auditory sequences, a person can be reading or watching a silent subtitled movie, yet still show a clear MMN.
[19] MMN is evoked by an infrequently presented stimulus ("deviant"), differing from the frequently-occurring stimuli ("standards") in one or several physical parameters like duration, intensity, or frequency.
Also the temporal order reversals elicit an MMN when successive sound elements differ either in frequency, intensity, or duration.
The MMN data can be understood as providing evidence that stimulus features are separately analysed and stored in the vicinity of auditory cortex (for a discussion, please see the theory section below).
Presently, the accumulated body of evidence suggests that while the MMN offers unique opportunities to basic research of the information processing of a healthy brain, it might be useful in tapping neurodegenerative changes as well.
Recent results suggest that a major problem underlying the reading deficit in dyslexia might be an inability of the dyslexics' auditory cortex to adequately model complex sound patterns with fast temporal variation.
Alzheimer's patients demonstrate decreased amplitude of MMN, especially with long inter-stimulus intervals; this is thought to reflect reduced span of auditory sensory memory.
This latter, seemingly contradictory, finding could be explained by hyperexcitability of CNS neurones resulting from neuroadaptive changes taking place during a heavy drinking bout.
A focus of research in the late 1990s aimed to tackle some of the key signal-analysis problems encountered in development of clinical use of MMN and challenges still remain.
[28] The mainstream "memory trace" interpretation of MMN is that it is elicited in response to violations of simple rules governing the properties of information.
It is thought to arise from violation of an automatically formed, short-term neural model or memory trace of physical or abstract environmental regularities.
[citation needed] Integral to this memory trace view is that there are: i) a population of sensory afferent neuronal elements that respond to sound, and; ii) a separate population of memory neuronal elements that build a neural model of standard stimulation and respond more vigorously when the incoming stimulation violates that neural model, eliciting an MMN.