ISSN:0196-0202    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

This article reviews research on the relatively recently discovered event-related potential component, the mismatch negativity (MMN), which is of great potential interest for understanding central auditory function and various forms of its pathology. This change-specific response can serve as an accurate objective measure for central sound representations that form the basis, for instance, for correct hearing of speech. Deficiencies in the MMN may be related to different forms of deficits in central auditory processing.

ISSN:0196-0202    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

The mismatch negativity (MMN) is an automatic cortical evoked potential that signifies the brain's detection of acoustic change. In other words, the MMN reflects the neurophysiologic processes that underlie auditory discrimination. As such, the MMN provides an objective tool for evaluating central auditory mechanisms involved in speech perception.We are using the MMN to study the central auditory processes that encode acoustic changes important for speech perception in 1) normal-hearing adults and children, 2) individuals with impaired auditory systems (including persons with learning disabilities, attention deficit disorders, cochlear implants), and 3) an animal model. Specifically, we have demonstrated that the MMN provides information about the central processing of fine acoustic differences, the neuroanatomic pathways that encode acoustic change, central auditory processing in the presence of peripheral hearing deficits, and central auditory system plasticity, In addition, we have considered methodological challenges associated with measuring the MMN in individual subjects. Several methodological issues—including appropriate stimuli, stimulus presentation variables, the recording protocol and environment, and validation of the MMN in individuals—are discussed.

ISSN:0196-0202    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

Infrequent (“deviant”) sounds occurring in a sequence of repetitive (“standard”) sounds elicit an event-related brain potential (ERP) response called the mismatch negativity (MMN) even in the absence of attention to these sounds. MMN appears to be caused by a neuronal mismatch between the deviant auditory input and a sensory-memory trace representing the standard stimuli. This automatic mismatch process has presumably a central role in discrimination of changes in the acoustic environment outside the focus of attention. Thus, localizing cerebral generators of MMN might help identify brain mechanisms of auditory sensory memory and involuntary attention. This review summarizes results from studies aimed at localizing MMN generators on the basis of (1) scalp-distribution, (2) magnetoencephalographic (MEG), (3) intracranial, and (4) brain-lesion data. These studies indicate that a major MMN source is located in the auditory cortex. However, the exact location of this MMN generator appears to depend on which feature of a sound is changed (e.g., frequency, intensity, or duration), as well as on the complexity of the sound (e.g., a simple tone versus complex sound). Consequently, memory traces for different acoustic features, as well as for sounds of different complexity, might be located in different regions of auditory cortex. However, MMN appears to have generators in other brain structures, too. There is some evidence for contribution of frontal-lobe activity to the MMN, which might be related to the involuntary switching of attention to a stimulus change occurring outside the focus of attention. In addition, intracranial MMN recordings in animals suggest that at least in some species, MMN subcomponents also may be generated in the thalamus and hippocampus.

ISSN:0196-0202    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

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.

ISSN:0196-0202    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

ObjectiveTo determine whether there are physiological correlates of categorical perception.DesignHuman evoked potentials were recorded in response to computer-modified speech sounds from a nine-stimulus continuum between ha/ and Ida/. In the first experiment, subjects listened to trains composed of 52% ha/ or Ida/ and 6% of each of the other eight stimuli and classified the stimuli as “ban or "da.” In the second experiment, subjects read a book and ignored trains containing a standard stimulus (p = 80%) and two deviant speech sounds (p = 10% each), one within the same category as the standard and the other across the category-boundary. The third experiment was similar to the first except that the subject was reading. The fourth experiment compared the responses to stimuli that deviated from standards in terms of their phonemic category or intensity.ResultsAn N2-P3 complex was evoked by those stimuli in the more improbable category when the stimuli were attended to in the first experiment. In the second and third experiments, there was a clear mismatch negativity (MMN) for the across-category deviant stimuli when the standard stimulus came from the ha/ end of the continuum. However, when the standard stimulus came from the /da/ end of the continuum, there was no definite MMN. The overall frequency-content of our Ida/ stimulus was broader than that of the ha/ stimulus. A deviant stimulus from the Ida/ end of the continuum thus contained frequencies which were not present in the ha/-standard stimuli and these frequencies could elicit a MMN. In the fourth experiment the MMN evoked by a small change in intensity was much larger than that evoked by a change in phonemic category.ConclusionsThe N2-P3 complex accurately reflects the phonemic categorization of speech stimuli. The MMN evoked by changes in speech sounds may indicate the detection of acoustic rather than phonetic changes.

ISSN:0196-0202    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

This review summarizes a number of findings related to the generation, development, and diagnostic value of mismatch negativity (MMN). The animal analogue of MMN to frequency contrast can be observed in the primary and secondary auditory cortical and also in the association cortical recordings. It is shown that subcortical sensory specific and archicortical structures may also contribute to the processes involved. The results are more complex than would be predicted by the notion that only the primary system plays an active role in the comparison processes reflected by the MMN that and the nonprimary pathway acts only as a modulating influence. The fundamental nature of the brain functions reflected by MMN is suggested by the demonstration of MMN in sleep and anesthesia, though in limited conditions.The postnatal development of automatic stimulus comparison, as indexed by MMN, presents an isochronicity, contrary to other evoked potential components whose development is not complete until puberty. Thus, the MMN provides a stable measure for electrophysiological assessment of auditory perception. This possible diagnostic value of the MMN is shown in studies of aphasics which emphasize the nature of perceptual deficits in the processing various speech and nonspeech stimuli.

ISSN:0196-0202    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

There is wide interest in the clinical application of mismatch negativity (MMN) to assess discriminative capabilities in individuals whose auditory capacities are difficult to determine, including infants, young children and those with severe cognitive impairment. Before MMN can be used as a clinical electrophysiologic measure, it is necessary to establish that it can be reliably elicited in normal individuals. This chapter describes a detailed analysis of MMN recorded in a group of healthy 8-yr-old children to assess intrasubject and intersubject reliability of the response. We conclude that although statistically reliable results can be obtained with group data, and perhaps even in individuals when large numbers of stimuli can be delivered, the unfavorable signal to noise ratio of individual MMN data currently limits its clinical applicability. Suggestions for approaches to surmount these difficulties are presented for its eventual clinical usefulness.

ISSN:0196-0202    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

The mismatch negativity (MMN) recordings provide an objective measure of the preattentive, automatic auditory discrimination function. This article deals with issues central to the recording of the MMN and the interpretation of the results for clinical and electrodiagnostic purposes. The methods of acquiring as pure an MMN response as possible, i.e., one not contaminated by auditory cortical responses reflecting other functions, are discussed first. Second, other technical questions associated with the recording are reported on, e.g., what MMN parameters should be recorded and how, what is the smallest recordable MMN response, and what is the repeatability of the MMN recordings. Then, the effect of various physiological factors on the MMN (age, alertness, gender, topographic distribution of the MMN) is considered. The correlation between auditory discrimination performance and the MMN amplitude, observed in normal population, is dealt with. Finally, there is a short concluding overview on clinical findings of MMN recordings and discussion on their electrodiagnostic applications.

ISSN:0196-0202    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

For individuals with severe or profound hearing loss, electrical stimulation of surviving neural elements by a cochlear implant may partly restore a sensation of hearing. Determining the extent of restoration based on behavioral measures may be difficult, particularly when evaluating young children or individuals who have little or no experience with normal hearing. In normal-hearing individuals, an objective measure of sound discrimination may be obtained by studying the mismatch negativity (MMN) component of the auditory evoked potential. The MMN may be evoked by a number of physical differences in acoustic stimuli including duration and pitch. For cochlear implant users, analogous stimulus differences may be produced by changing the length of a stimulus pulse train or by changing the pair of activated electrodes along a multi-electrode implant array. This paper will provide an overview of our current results, comparing evoked response data recorded from both normal-hearing individuals and cochlear implant users. In both normal- hearing individuals and cochlear implant users, MMNs were evoked by differences in stimulus train duration and pitch (or electrode pair activation in cochlear implant users). These findings suggest that the MMN may be a useful method for assessing the discriminability of electrical stimulation patterns produced by a cochlear implant. Eventually, information gained by MMN testing may yield important information for developing rehabilitation programs for the individual user.

ISSN:0196-0202    

出版商:OVID    

年代:1995

数据来源: OVID