Los niños prematuros tienen un alto riesgo de dificultades en el procesamiento auditivo central, evidenciadas mediante los potenciales evocados auditivos / Children born preterm have high risk for central auditory processing deficits, as indexed by the auditory brain event-related potentials (ERPs)

Una parte importante del desarrollo cerebral y de las redes neuronales se produce durante las últimas 6 semanas de gestación. Por consiguiente, el cerebro inmaduro es muy susceptible a las consecuencias del nacimiento prematuro y a un desarrollo atípico de los procesos neurobiológicos. Se ha observado que el nacimiento pretérmino afecta con mayor frecuencia a la maduración del cerebro en las áreas frontal, temporal media y parietooccipital, que son importantes para los procesos auditivos, lingüísticos y cognitivos y para la integración de la información recibida. Muchos niños prematuros presentan deficiencias en el procesamiento auditivo central (PAC) a nivel de la codificación de los rasgos sonoros. Nuestros estudios de seguimiento muestran que los niños prematuros también presentaban déficit en la discriminación auditiva central, medida a través del potencial de disparidad (MMN, del inglés mismatch negativity). Además, los déficit en la discriminación auditiva central se correlacionaban con la adquisición del lenguaje. Estos déficit persisten, con frecuencia, desde la primera infancia hasta la edad escolar. Por estos motivos, se debería evaluar el PAC desde una edad temprana para poder organizar una rehabilitación oportuna y específica para este tipo de trastorno (AU)

A significant proportion of brain development and networking occurs during the last six weeks of gestation. Therefore, the immature brain is highly susceptible to the consequences of preterm birth, and atypical timing of neurobiological processes. It has been shown that preterm birth impairs brain maturation most frequently in the frontal as well as mid-temporal and parieto-occipital cortices that are important for auditory, language and cognitive processes and for integration of the information received. Many children born preterm have deficits in central auditory processing (CAP) at the level of sound feature encoding. Our follow-up studies showed that children born preterm have also deficits at the level of central auditory discrimination, as indexed by the mismatch negativity (MMN). Furthermore, deficits in central auditory discrimination correlated with language acquisition. These deficits often persist from infancy up to school age. For these reasons CAP should be evaluated from early age on to arrange timely and disorder specific rehabilitation (AU)

Similarities in the phenotype of the auditory neural substrate in children with Asperger syndrome and their parents.

Asperger syndrome (AS) is a developmental disorder of brain function characterized by deficits in social interaction including difficulties in understanding emotional expressions. Children with AS share some of the behavioural characteristics with their parents and AS seems to run particularly in the male members of the same families. The aim of the present study was to determine whether similarities could be found between children with AS and their parents at central auditory processing. It was found that in children with AS the sound encoding, as reflected by the exogenous components of event-related potentials, was similarly abnormal as in both their mothers and fathers. However, their abnormal cortical auditory discrimination, as indexed by the prolonged latency of the mismatch negativity, resembled that of their fathers but not that of their mothers. The present results suggest that complex genetic mechanisms may contribute to auditory abnormalities encountered in children with AS.

Early and late mismatch negativity elicited by words and speech-like stimuli in children.

In auditory perception the brain's attentional and preattentional mechanisms select certain stimuli for preferential processing and filter out irrelevant input. This study investigated nonattentive auditory processing in children. Event-related potentials (ERPs) provide a means to study neural correlates related to language and speech-sound processing. Mismatch negativity (MMN) is an ERP wave that indicates attention-independent perceptual change detection. In this study cortical ERPs were elicited by complex tones, naturally spoken words, and pseudowords, with each stimulus type containing equal acoustical elements. Tones elicited a bifurcated mismatch negativity (MMN), with early MMN (peaking at 150-200 ms) being more dominant. On the other hand, words elicited a strong late MMN, peaking at about 400-450 ms after stimulus onset. The MMN wave form was significantly weaker for pseudowords than for words. The late MMN wave, especially for word differences, was found to reflect summating MMN generators and memory trace formation on gestalt bases. Results suggest that the auditory processing, even nonattended, is highly associated with the cognitive meaning of the stimuli.

Mismatch negativity and late discriminative negativity in investigating speech perception and learning in children and infants.

For decades, behavioral methods, such as the head-turning or sucking paradigms, have been the primary tools to investigate speech perception and learning of a language in infancy. Recently, however, new methods provided by event-related potentials have emerged. These are called mismatch negativity (MMN) and late discriminative negativity (LDN). MMN, the brain's automatic change-detection response in audition, has been intensively used in adults in both basic and clinical studies for longer than 20 years. LDN, on the other hand, was only recently discovered. There seem to be many differences between these two responses. MMN is developmentally quite stable and can be obtained even from preterm infants. LDN, however, can be obtained most reliably from young children, and its amplitude decreases as a function of age. New data suggest that both of these responses have a special role in language processing, although both of them can also be elicited by nonspeech stimuli.

Automatic auditory word perception as measured by 40 Hz EEG responses.

OBJECTIVES: Here we report the existence of automatic speech perception in man, revealed by 40 Hz EEG responses. METHODS: We presented to Finnish subjects the Finnish word /tu:li/(wind) as the standard stimulus and another Finnish word /tuli/(fire) as the deviant stimulus using a passive auditory oddball task. The experiment was also conducted with pseudowords as stimuli. RESULTS: We observed a global significant increase in 40 Hz EEG power at 600 ms after stimulus onset for words, but not for pseudowords. CONCLUSIONS: Our results indicate that the memory representation of the standard verbal stimuli, even if unattended, might not merely be based on the physical features of the stimuli: if a semantic representation exists, then the brain processes it pre-attentively.

Abnormal frequency mismatch negativity in mentally retarded children and in children with developmental dysphasia.

The auditory event-related potential waveform termed "mismatch negativity" was examined in 12 mentally retarded children with delayed development of speech and language (aged 5-8 years) and in 13 children with developmental dysphasia (aged 5-9 years). The mismatch negativity waves were elicited with pure sine-wave tone stimuli using the oddball paradigm. We measured the peak latency and peak amplitude of mismatch negativity responses to frequency (500/553 Hz) difference. The mismatch negativity patterns were compared with those of 10 children with normal development of linguistic skills (aged 5-9 years). In both the mentally retarded and dysphasic groups, the peak amplitude of the frequency mismatch negativity was significantly attenuated when compared with the control group, but no significant difference was observed between the mentally retarded and dysphasic groups. Attenuated frequency mismatch negativity was related to impairment of linguistic skills irrespective of the child's cognitive skills. Because the mismatch negativity response reflects central auditory processing and is modal specific for auditory stimuli, this change-specific response can serve as an objective tool to elucidate central auditory deficits in children.

Attenuated auditory event-related potential (mismatch negativity) in children with developmental dysphasia.

An attention-independent negative wave-form termed 'mismatch negativity' (MMN) of the auditory event-related potentials (ERPs) was studied in ten children (3-6 years) with developmental dysphasia and in fourteen control children (3-7 years) with normal speech and language development. The MMNs were elicited with pure sine tone stimuli using the oddball paradigm. The peak latency and peak amplitude of MMN response to frequency (500/553 H2) difference was measured. The grand average amplitude of frequency MMN was significantly attenuated in dysphasic children as compared to controls, but no significant difference was observed in the latency of peak frequency MMN. The results indicate that dysphasic children have a defect in automatic auditory processing of frequency differences. Because the MMN response reflects central auditory processing and is modal specific for auditory stimuli we argue that the MMN method can serve as an objective tool to assess central auditory deficits in children.

Practical issues in the clinical application of mismatch negativity.

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.

Auditory ERP components and mismatch negativity in dysphasic children.

Auditory event-related potentials (ERPs) and especially the mismatch negativity component (MMN) were examined in 14 dysphasic and 12 normal children (aged 7-13). The ERPs were elicited by sine tone stimuli using the passive oddball paradigm and short ISI (350 msec). We measured the peak latency and peak amplitude of MMN responses to frequency (500/553 Hz) and duration (50/110 msec or 50/500 msec) differences. In the dysphasic group the peak amplitude of the frequency MMN was significantly attenuated. The duration MMN showed a significant difference between the two groups only for stimuli with highly contrasting values (50/500 msec). In normal subjects we found a negative correlation between the peak latency of the frequency MMN and age. The maturational changes of long-latency ERPs were non-significant in dysphasic children. Evidence of differences in hemispheric asymmetry between the two groups was observed.