Mismatch negativity

The mismatch negativity (MMN) or mismatch field (MMF) is a component of the event-related potential (ERP) to an odd stimulus in a sequence of stimuli. It arises from electrical activity in the brain and is studied within the field of cognitive neuroscience and psychology. It can occur in any sensory system, but has most frequently been studied for hearing and for vision. In the case of auditory stimuli, the MMN occurs after an infrequent change in a repetitive sequence of sounds (sometimes the entire sequence is called an oddball sequence.) For example, a rare deviant (d) sound can be interspersed among a series of frequent standard (s) sounds (e.g., s s s s s s s s s d s s s s s s d s s s d s s s s...). The deviant sound can differ from the standards in one or more perceptual features such as pitch, duration, or loudness. The MMN is usually evoked by either a change in frequency, intensity, duration or real or apparent spatial locus of origin. The MMN can be elicited regardless of whether the subject is paying attention to the sequence. During auditory sequences, a person can be reading or watching a silent subtitled movie, yet still show a clear MMN. In the case of visual stimuli, the MMN occurs after an infrequent change in a repetitive sequence of images. The mismatch negativity (MMN) or mismatch field (MMF) is a component of the event-related potential (ERP) to an odd stimulus in a sequence of stimuli. It arises from electrical activity in the brain and is studied within the field of cognitive neuroscience and psychology. It can occur in any sensory system, but has most frequently been studied for hearing and for vision. In the case of auditory stimuli, the MMN occurs after an infrequent change in a repetitive sequence of sounds (sometimes the entire sequence is called an oddball sequence.) For example, a rare deviant (d) sound can be interspersed among a series of frequent standard (s) sounds (e.g., s s s s s s s s s d s s s s s s d s s s d s s s s...). The deviant sound can differ from the standards in one or more perceptual features such as pitch, duration, or loudness. The MMN is usually evoked by either a change in frequency, intensity, duration or real or apparent spatial locus of origin. The MMN can be elicited regardless of whether the subject is paying attention to the sequence. During auditory sequences, a person can be reading or watching a silent subtitled movie, yet still show a clear MMN. In the case of visual stimuli, the MMN occurs after an infrequent change in a repetitive sequence of images. MMN refers to the mismatch response in electroencephalography (EEG); MMF or MMNM refer to the mismatch response in magnetoencephalography (MEG). The auditory MMN was discovered in 1978 by Risto Näätänen, A. W. K. Gaillard, and S. Mäntysalo at the Institute for Perception, TNO in The Netherlands. The first report of a visual MMN was in 1990 by Rainer Cammer. For a history of the development of the visual MMN, see Pazo-Alvarez et al. (2003). The MMN is a response to a deviant within a sequence of otherwise regular stimuli; thus, in an experimental setting, it is produced when stimuli are presented in a many-to-one ratio; for example, in a sequence of sounds s s s s s s s d s s s s d s s s..., the d is the deviant or oddball stimulus, and will elicit an MMN response. The mismatch negativity occurs even if the subject is not consciously paying attention to the stimuli. Processing of sensory stimulus features is essential for humans in determining their responses and actions. If behaviourally relevant aspects of the environment are not correctly represented in the brain, then the organism's behaviour cannot be appropriate. Without these representations our ability to understand spoken language, for example, would be seriously impaired. Cognitive neuroscience has consequently emphasised the importance of understanding brain mechanisms of sensory information processing, that is, the sensory prerequisites of cognition. Most of the data obtained, unfortunately, do not allow the objective measurement of the accuracy of these stimulus representations (see Näätänen, 1992). In addition, recent cognitive neuroscience seems to have succeeded in extracting such a measure, however. This is the mismatch negativity (MMN), a component of the event-related potential (ERP), first reported by Näätänen, Gaillard, and Mäntysalo (1978). An in-depth review of MMN research can be found in Näätänen (1992) while other recent reviews also provide information on the generator mechanisms of MMN (Alho 1995), its magnetic counterpart, MMNm (Näätänen, Ilmoniemi & Alho, 1994), and its clinical applicability (Näätänen & Alho, 1995). The auditory MMN can occur in response to deviance in pitch, intensity, or duration. The auditory MMN is a fronto-central negative potential with sources in the primary and non-primary auditory cortex and a typical latency of 150-250 ms after the onset of the deviant stimulus. Sources could also include one from the right opercular part of the inferior frontal gyrus. The amplitude and latency of the MMN is related to how different the deviant stimulus is from the standard. Large deviances elicit MMN at earlier latencies. For very large deviances, the MMN can even overlap the N100 (e.g., Campbell et al., 2007). The visual MMN can occur in response to deviance in such aspects as color, size, or duration. The visual MMN is an occipital negative potential with sources in the primary visual cortex and a typical latency of 150-250 ms after the onset of the deviant stimulus. As kindred phenomena have been elicited with speech stimuli, under passive conditions that require very little active attention to the sound, a version of MMN has been frequently used in studies of neurolinguistic perception, to test whether or not these participants neurologically distinguish between certain kinds of sounds. The MMN response has been used to study how fetuses and newborns discriminate speech sounds. In addition to these kinds of studies focusing on phonological processing, some research has implicated the MMN in syntactic processing. Some of these studies have attempted to directly test the automaticity of the MMN, providing converging evidence for the understanding of the MMN as a task-independent and automatic response. 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 (Näätänen, 1992). In addition, it is generated by a change in spectrally complex stimuli like phonemes, in synthesised instrumental tones, or in the spectral component of tone timbre. Also the temporal order reversals elicit an MMN when successive sound elements differ either in frequency, intensity, or duration. The MMN is not elicited by stimuli with deviant stimulus parameters when they are presented without the intervening standards. Thus, the MMN has been suggested to reflect change detection when a memory trace representing the constant standard stimulus and the neural code of the stimulus with deviant parameter(s) are discrepant.