Mismatch Negativity Event-related Potential Research Articles

A Clinical Electrophysiological Study of Emotional Lability in Patients With Systemic Lupus Erythematosus

A Clinical Electrophysiological Study of Emotional Lability in Patients With Systemic Lupus Erythematosus

Cerebral Responses to Change in Spatial Location of Unattended Sounds

The neural basis of spatial processing in the auditory cortex has been controversial. Human fMRI studies suggest that a part of the planum temporale (PT) is involved in auditory spatial processing, but it was recently argued that this region is active only when the task requires voluntary spatial localization. If this is the case, then this region cannot harbor an ongoing spatial representation of the acoustic environment. In contrast, we show in three fMRI experiments that a region in the human medial PT is sensitive to background auditory spatial changes, even when subjects are not engaged in a spatial localization task, and in fact attend the visual modality. During such times, this area responded to rare location shifts, and even more so when spatial variation increased, consistent with spatially selective adaptation. Thus, acoustic space is represented in the human PT even when sound processing is not required by the ongoing task.

Phonological deficit in school children is reflected in the Mismatch Negativity

Deficits in processing of auditory stimuli are known to play an important role in the aetiology of dyslexia. To specify the auditory deficit in children at risk for dyslexia, 19 children with a phonological deficit and 15 controls were tested using the mismatch negativity event-related potential, which reflects preattentive auditory processing. Children with a phonological deficit, not yet suffering from dyslexia, had similar mismatch negativity patterns to dyslexics. The deficit was speech specific, because there were significant group differences only with syllables but not with pure tones.

Visual temporal window of integration as revealed by the visual mismatch negativity event-related potential to stimulus omissions

We studied whether, similarly to the auditory modality, short-period temporal integration processes occur in vision. Event-related potentials (ERP) were recorded for occasional stimulus omissions from sequences of patterned visual stimuli. A posterior negative component emerged only when the constant stimulus onset asynchrony (SOA) was shorter than 150 ms. This upper limit is comparable with the duration of the temporal window of integration observed in the auditory modality (including experiments studying the effects of stimulus omissions). Parameters of the posterior negativity were highly similar irrespective of whether the stimuli were task-relevant or not (Experiment 1). Thus, we identified this potential as the visual mismatch negativity (vMMN) component, which reflects task-independent detection of violating regularities of the stimulation. vMMN was followed by an anterior positivity (the P3a), indicating attentional shifts induced by the stimulus omissions. In Experiment 2, a posterior negativity similar to that observed in Experiment 1 emerged after the termination of short trains of stimuli, again only when the SOA was shorter than 150 ms. These results support the notion of a temporal integration window in the visual modality, the duration of which is between 150 and 180 ms.

Object representation in the human auditory system

One important principle of object processing is exclusive allocation. Any part of the sensory input, including the border between two objects, can only belong to one object at a time. We tested whether tones forming a spectro-temporal border between two sound patterns can belong to both patterns at the same time. Sequences were composed of low-, intermediate- and high-pitched tones. Tones were delivered with short onset-to-onset intervals causing the high and low tones to automatically form separate low and high sound streams. The intermediate-pitch tones could be perceived as part of either one or the other stream, but not both streams at the same time. Thus these tones formed a pitch 'border' between the two streams. The tones were presented in a fixed, cyclically repeating order. Linking the intermediate-pitch tones with the high or the low tones resulted in the perception of two different repeating tonal patterns. Participants were instructed to maintain perception of one of the two tone patterns throughout the stimulus sequences. Occasional changes violated either the selected or the alternative tone pattern, but not both at the same time. We found that only violations of the selected pattern elicited the mismatch negativity event-related potential, indicating that only this pattern was represented in the auditory system. This result suggests that individual sounds are processed as part of only one auditory pattern at a time. Thus tones forming a spectro-temporal border are exclusively assigned to one sound object at any given time, as are spatio-temporal borders in vision.

Spatial asymmetries of auditory event-synthesis in humans

We used the mismatch negativity event-related potential to examine how spatial location and feature variation affect the capacity of the auditory system to automatically respond to pairs of rapid (180 ms apart) acoustic changes within a single tone. When a tone first deviated from a standard tone in source location and then in its duration, we found independent responses to both deviations for right but not left field stimuli. In contrast, when the first deviation was in pitch and the second in duration, only the first deviation elicited a response, regardless of presentation side. These results suggest that information from either side of space is asymmetrically processed even in a free-field, and that the extent of the temporal window of integration is not a fixed property of the auditory system.

Effect of propofol anaesthesia on the event-related potential mismatch negativity and the auditory-evoked potential N1

Studies on the effects of anaesthesia on event-related potentials and long latency auditory-evoked potentials (AEP) are sparse. Both provide information on cortical processing and may have potential as monitors of awareness. We studied the effect of propofol on the event-related potential mismatch negativity (MMN) and the long-latency AEP NI. Twenty-one patients received 1 microgram ml-1 stepped increases in the target concentration of propofol using Diprifusor until a maximum of 6 micrograms ml-1 was achieved or the patient had lost consciousness. Neurophysiological responses (MMN and N1) and the patients' level of consciousness were recorded before the administration of propofol and at a target effector site concentration of propofol of 1, 2, 3, 4, and 6 micrograms ml-1. Grand average evoked potentials were computed at baseline, before the administration of propofol (A); at the highest propofol concentration at which each patient was responsive (B); and at the concentration of propofol at which the patient became unconscious (C). Patients lost consciousness at different target concentrations of propofol, all being unresponsive by 4 micrograms ml-1. The response to the deviant stimuli used to elicit duration-shift MMN was significantly more negative than to the standard stimuli at A (mean difference 2.58 microV, P = 0.0011) but this difference was virtually abolished at point B, before the patients lost consciousness (mean difference 0.63 microV, P = ns). The amplitude of N1 evoked by standard stimuli was negative compared with electrical baseline at both point A (mean amplitude -3.81 microV, P < 0.001) and at point B (mean amplitude -2.2 microV, P = 0.002), but was no longer significantly different to baseline at point C (mean amplitude 0.51 microV, P = ns). The change in the mean amplitude of N1 from last awake (point B) to first unconscious (point C) was also significant (mean difference in amplitude 1.69 microV, P = 0.02). MMN is unlikely to be a clinically useful tool to detect awareness in surgical patients. In contrast, the loss of N1 may identify the transition from consciousness to unconsciousness and deserves further study.

Effect of propofol anaesthesia on the event-related potential mismatch negativity and the auditory-evoked potential N1

Effect of propofol anaesthesia on the event-related potential mismatch negativity and the auditory-evoked potential N1

A comparison of the mismatch negativity (MMN) event-related potential to tone and speech stimuli in normal and aphasic adults

We evaluated the mismatch negativity (MMN) event-related potential (ERP) in normal and aphasic adults to tone and speech stimuli to determine aphasic patients' auditory discrimination and the relationship between MMN measures and severity of aphasia. MMNs were present in 89% of normal subjects and 79% of aphasic subjects to tone stimuli. MMNs were present in 100% of normal subjects and 54% of aphasic subjects to speech stimuli. The duration of the MMN ERP to speech stimuli was significantly related to severity of aphasia on the Western Aphasia Battery, Porch Index of Communicative Ability, and the Token Test. Thus, not all aphasic people show an early, preconscious orientation response to tone and speech stimuli. However, the duration of this response, when present, to speech stimuli appears to be related to the severity of aphasia.

Feature conjunctions and auditory sensory memory

This study sought to obtain additional evidence that transient auditory memory stores information about conjunctions of features on an automatic basis. The mismatch negativity of event-related potentials was employed because its operations are based on information that is stored in transient auditory memory. The mismatch negativity was found to be elicited by a tone that differed from standard tones in a combination of its perceived location and frequency. The result lends further support to the hypothesis that the system upon which the mismatch negativity relies processes stimuli in an holistic manner.

Adaptive modeling of the unattended acoustic environment reflected in the mismatch negativity event-related potential

The mismatch negativity (MMN) event-related potential is elicited by changes in repetitive auditory stimuli. The present paper suggests that: (1) an acoustic model of the auditory environment is maintained even in the absence of attention focussed on auditory stimuli, preattentively detecting repetitive features of the acoustic stimulation; and (2) the MMN reflects modifications to existing parts of this model during incorporation of a new stimulus into the model. MMN responses were investigated during the period when a repetitive stimulus (standard) was replaced by a new standard sound. It was found that whereas the new standard stimulus stopped eliciting an MMN after its third presentation with respect to the old standard, a probe stimulus, differing from both standards, elicited an MMN with respect to the old standard, even when following four presentations of the new standard. The probe stimulus also elicited an MMN with respect to the new standard after four or more presentations of this new standard stimulus, thus eliciting two consecutive MMNs. The comparison (conducted on the basis of the present and some previous findings) of the present hypothesis with alternative explanations of MMN based on the presence and strength of auditory transient memory traces supported the model adjustment hypothesis.

The Mismatch Negativity of Event-Related Potentials as a Probe of Transient Auditory Memory

The use of the mismatch negativity as a probe to study the memory upon which it depends is reviewed. Topics about the memory include its duration, its capacity, the kind of information that can be stored in the memory, how the information is stored, whether the memory is accessed in parallel or in series, whether it is hard-wired or can be modified by experience, and its relationship to sensory memory.

Mismatch negativity in school-age children to speech stimuli that are just perceptibly different

The mismatch negativity event-related potential (MMN) was elicited in normal school-age children in response to just perceptibly different variants of the speech phoneme /da/. A significant MMN was measured in each subject tested. Child and adult MMNs were similar with respect to peak latency and duration. Measures of MMN magnitude (peak-to-peak amplitude and area) were significantly larger in children than in adults. The results of the present study indicate that the MMN can be elicited in response to minimal acoustic stimulus differences in complex speech signals in school-age children. The results support the feasibility of using the MMN as a tool in the study of deficient auditory perception in children.

Acoustic versus phonetic representation of speech as reflected by the mismatch negativity event-related potential

The concept of categorical perception of speech and speech-like sounds has been central to models of speech perception for decades. Event-related potentials (ERPs) provide a neurophysiologic perspective of this important phenomenon. In the present experiment the mismatch negativity (MMN) event-related potential, which is sensitive to fine acoustic differences, was recorded in adults. Of interest was whether the MMN reflects the acoustic or categorical perception of speech. The MMN was elicited by stimulus pairs (along a continuum varying in place of articulation from /da/ to /ga/) which had been identified as the same phoneme /da/ (within category condition) and as different phonemes /da/ and /ga/ (across categories condition). The acoustic differences between these two pairs of stimuli were equivalent. The MMN was observed in all subjects both in the within and across category conditions. Furthermore, the MMN did not differ in latency, amplitude or area within and across categories. That is, the MMN indicated equal discrimination both across and within categories. These results suggest that the MMN appears to reflect the processing of acoustic aspects of the speech stimulus, but not phonetic processing into categories. The MMN appears to be an extremely sensitive electrophysiologic index of minimal acoustic differences in speech stimuli.