Auditory evoked responses during the first year of life

Development of Auditory Evoked Responses in Normally Developing Preschool Children and Children with Autism Spectrum Disorder

The cortical responses to auditory stimuli undergo rapid and dramatic changes during the first 3 years of life in normally developing (ND) children, with decreases in latency and changes in amplitude in the primary peaks. However, most previous studies have focused on children >3 years of age. The analysis of data from the early stages of development is challenging because the temporal pattern of the evoked responses changes with age (e.g., additional peaks emerge with increasing age) and peak latency decreases with age. This study used the topography of the auditory evoked magnetic field (AEF) to identify the auditory components in ND children between 6 and 68 months (n = 48). The latencies of the peaks in the AEF produced by a tone burst (ISI 2 ± 0.2 s) during sleep decreased with age, consistent with previous reports in awake children. The peak latencies of the AEFs in ND children and children with autism spectrum disorder (ASD) were compared. Previous studies indicate that the latencies of the initial components of the auditory evoked potential (AEP) and the AEF are delayed in children with ASD when compared to age-matched ND children >4 years of age. We speculated whether the AEF latencies decrease with age in children diagnosed with ASD as in ND children, but with uniformly longer latencies before the age of about 4 years. Contrary to this hypothesis, the peak latencies did not decrease with age in the ASD group (24-62 months, n = 16) during sleep (unlike in the age-matched controls), although the mean latencies were longer in the ASD group as in previous studies. These results are consistent with previous studies indicating delays in auditory latencies, and they indicate a different maturational pattern in ASD children and ND children. Longitudinal studies are needed to confirm whether the AEF latencies diverge with age, starting at around 3 years, in these 2 groups of children.

Dynamics of infant cortical auditory evoked potentials (CAEPs) for tone and speech tokens

OBJECTIVES

Cortical auditory evoked potentials (CAEPs) to tones and speech sounds were obtained in infants to: (1) further knowledge of auditory development above the level of the brainstem during the first year of life; (2) establish CAEP input-output functions for tonal and speech stimuli as a function of stimulus level and (3) elaborate the data-base that establishes CAEP in infants tested while awake using clinically relevant stimuli, thus providing methodology that would have translation to pediatric audiological assessment. Hypotheses concerning CAEP development were that the latency and amplitude input-output functions would reflect immaturity in encoding stimulus level. In a second experiment, infants were tested with the same stimuli used to evoke the CAEPs. Thresholds for these stimuli were determined using observer-based psychophysical techniques. The hypothesis was that the behavioral thresholds would be correlated with CAEP input-output functions because of shared cortical response areas known to be active in sound detection.

DESIGN

36 infants, between the ages of 4 and 12 months (mean=8 months, s.d.=1.8 months) and 9 young adults (mean age 21 years) with normal hearing were tested. First, CAEPs amplitude and latency input-output functions were obtained for 4 tone bursts and 7 speech tokens. The tone bursts stimuli were 50 ms tokens of pure tones at 0.5, 1.0, 2.0 and 4.0 kHz. The speech sound tokens, /a/, /i/, /o/, /u/, /m/, /s/, and /∫/, were created from natural speech samples and were also 50 ms in duration. CAEPs were obtained for tone burst and speech token stimuli at 10 dB level decrements in descending order from 70 dB SPL. All CAEP tests were completed while the infants were awake and engaged in quiet play. For the second experiment, observer-based psychophysical methods were used to establish perceptual threshold for the same speech sound and tone tokens.

RESULTS

Infant CAEP component latencies were prolonged by 100-150 ms in comparison to adults. CAEP latency-intensity input output functions were steeper in infants compared to adults. CAEP amplitude growth functions with respect to stimulus SPL are adult-like at this age, particularly for the earliest component, P1-N1. Infant perceptual thresholds were elevated with respect to those found in adults. Furthermore, perceptual thresholds were higher, on average, than levels at which CAEPs could be obtained. When CAEP amplitudes were plotted with respect to perceptual threshold (dB SL), the infant CAEP amplitude growth slopes were steeper than in adults.

CONCLUSIONS

Although CAEP latencies indicate immaturity in neural transmission at the level of the cortex, amplitude growth with respect to stimulus SPL is adult-like at this age, particularly for the earliest component, P1-N1. The latency and amplitude input-output functions may provide additional information as to how infants perceive stimulus level. The reasons for the discrepancy between electrophysiologic and perceptual threshold may be due to immaturity in perceptual temporal resolution abilities and the broad-band listening strategy employed by infants. The findings from the current study can be translated to the clinical setting. It is possible to use tonal or speech sound tokens to evoke CAEPs in an awake, passively alert infant, and thus determine whether these sounds activate the auditory cortex. This could be beneficial in the verification of hearing aid or cochlear implant benefit.

Potencial evocado auditivo de longa latência para estímulo de fala apresentado com diferentes transdutores em crianças ouvintes

Objetivo: analisar, de forma comparativa, a influência do transdutor no registro dos componentes P1, N1 e P2 eliciados por estímulo de fala, quanto à latência e à amplitude, em crianças ouvintes. Método: 30 crianças ouvintes de quatro a 12 anos de idade, de ambos os sexos. Os potenciais evocados auditivos de longa latência foram pesquisados por meio dos transdutores, fone de inserção e caixa acústica, eliciados por estímulo de fala /da/, sendo o intervalo interestímulos de 526ms, a intensidade de 70dBNA e a taxa de apresentação de 1,9 estímulos por segundo. Foram analisados os componentes P1, N1 e P2 quando presentes, quanto à latência e à amplitude. Resultados: constatou-se um nível de concordância forte entre a pesquisadora e o juiz. Não houve diferença estatisticamente significante ao comparar os valores de latência e amplitude dos componentes P1, N1 e P2, ao considerar sexo e orelha, assim como para a latência dos componentes quando analisado os tipos de transdutores. Entretanto, houve diferença estatisticamente significante para a amplitude dos componentes P1 e N1, com maior amplitude para o transdutor caixa acústica. Conclusão: os valores de latência dos componentes P1, N1 e P2 e amplitude de P2 obtidos com fone de inserção podem ser utilizados como referência de normalidade independente do transdutor utilizado para a pesquisa dos potenciais evocados auditivos de longa latência.

Speech perception and cortical auditory evoked potentials in cochlear implant users with auditory neuropathy spectrum disorders

OBJECTIVE

To characterize the P(1) component of long latency auditory evoked potentials (LLAEPs) in cochlear implant users with auditory neuropathy spectrum disorder (ANSD) and determine firstly whether they correlate with speech perception performance and secondly whether they correlate with other variables related to cochlear implant use.

METHODS

This study was conducted at the Center for Audiological Research at the University of São Paulo. The sample included 14 pediatric (4-11 years of age) cochlear implant users with ANSD, of both sexes, with profound prelingual hearing loss. Patients with hypoplasia or agenesis of the auditory nerve were excluded from the study. LLAEPs produced in response to speech stimuli were recorded using a Smart EP USB Jr. system. The subjects' speech perception was evaluated using tests 5 and 6 of the Glendonald Auditory Screening Procedure (GASP).

RESULTS

The P(1) component was detected in 12/14 (85.7%) children with ANSD. Latency of the P(1) component correlated with duration of sensorial hearing deprivation (*p=0.007, r=0.7278), but not with duration of cochlear implant use. An analysis of groups assigned according to GASP performance (k-means clustering) revealed that aspects of prior central auditory system development reflected in the P(1) component are related to behavioral auditory skills.

CONCLUSIONS

In children with ANSD using cochlear implants, the P(1) component can serve as a marker of central auditory cortical development and a predictor of the implanted child's speech perception performance.

Maturation of auditory evoked potentials from 6 to 48 months: prediction to 3 and 4 year language and cognitive abilities

OBJECTIVE

To investigate the maturation of long-latency auditory evoked potentials (LLAEP) from 6 to 48 months in infants with a family history of language impairment (FH+) and control infants (FH-).

METHODS

LLAEPs of seventeen FH+ infants were compared to 28 FH- infants at 6, 9, 12, 16, 24, 36 and 48 months. Participants received a passive oddball paradigm using fast- and slow-rate non-linguistic auditory stimuli and at 36 and 48 months completed a battery of standardized language and cognitive tests.

RESULTS

Overall, the morphology of LLAEP responses differed for fast- versus slow-rate stimuli. Significant age-related changes in latency and amplitude were observed. Group differences, favoring FH- infants, in the rate of maturation of LLAEPs were found. Responses to fast-rate stimuli predicted language abilities at 36 and 48 months of age.

CONCLUSIONS

The development of LLAEP in FH+ children is modulated by differences in the rate of maturation as well as variations in temporal processing abilities.

SIGNIFICANCE

These findings provide evidence for the role of non-linguistic auditory processes in early language development and illustrate the utility of using a perceptual-processing skills model to further our understanding of the precursors of language development and impairment.

Early Maturation of Frequency-Following Responses to Voice Pitch in Infants with Normal Hearing

Neural plasticity of pitch processing mechanisms at the human brainstem, as reflected by the scalp-recorded frequency-following response (FFR) to voice pitch, has been reported for normal-hearing adults. Characteristics and maturation of such a response during the first year of life have remained unclear. The purpose of this study was to examine the characteristics of FFR to voice pitch in normal-hearing infants and to make a direct comparison with adults using the same stimulus and recording parameters. 9 infants and 9 adults were recruited. A Chinese monosyllable that mimics the English vowel /i/ with a rising pitch was used to elicit the FFR to voice pitch. The results demonstrated that infant FFRs showed slightly larger Pitch Strength but comparable Frequency Error, Slope Error, and Tracking Accuracy to those obtained from adults. Early maturation of FFRs was also observed in the infants starting from 1 to 3 mo. of age.

Protocol to collect late latency auditory evoked potentials

Long Latency Auditory Evoked Potentials (LLAEP) represents a number of electrical changes occurring in the central nervous system, resulting from stimulation of the auditory sensorial pathways. Many studies approach the use of these potentials controlling the artifact created by eye movement with the use of equipment with a large number of channels. However, what happens is very different in Brazilian clinical practice, where the equipment used has a very limited number of channels.

Aim

to compare the two methods used to control the artifacts created by eye movements during LLAEP capture using two recording channels.

Materials and Methods

this is a prospective study with the application of two LLAEP capturing methods (eye artifact subtraction and rejection limit control) in 10 normal hearing individuals.

Results

we did not observe statistically significant differences concerning the latency values obtained with the use of both methods, only concerning amplitude values.

Conclusion

both methods were efficient to capture the LLAEP and to control the eye movement artifact. The rejection limit control method produced greater amplitude values.

In defense of qualitative changes in development

The balance between the preservation of early cognitive functions and serious transformations on these functions shifts across time. Piaget's writings, which favored transformations, are being replaced by writings that emphasize continuities between select cognitive functions of infants and older children. The claim that young infants possess elements present in the older child's concepts of number, physical impossibility, and object permanence is vulnerable to criticism because the inferences are based primarily on the single measure of change in looking time. It is suggested that investigators use unique constructs to describe phenomena observed in young infants that appear, on the surface, to resemble the psychological competences observed during later developmental stages.

Change detection in newborns using a multiple deviant paradigm: a study using magnetoencephalography

OBJECTIVE

Mismatch responses are elicited to changes in sound streams in healthy newborns. In the ideal case, these responses can predict cognitive problems later in life. We employed a multiple deviant paradigm for a fast assessment of the ability of the newborn brain to respond to various types of acoustic changes.

METHODS

In 12 healthy newborns, we recorded an electroencephalogram (EEG) and magnetoencephalogram while presenting auditory stimuli. Between repeated stimuli, four types of acoustic changes (frequency, intensity, duration, and a gap) were presented, varying in deviance magnitude.

RESULTS

One major response was present in the neonatal evoked potentials and fields at 250-260 ms. Magnetic mismatch responses were elicited to all change types except for the duration deviant and they were positive in polarity. The frequency deviant elicited more positive EEG amplitudes than the standard, whereas the response to the duration deviant was more negative.

CONCLUSIONS

These results show that newborns can detect changes to at least four types of deviances within a sound stream. Furthermore, the use of magneto- and electroencephalography is complementary in newborns, since the methods may reveal different outcomes.

SIGNIFICANCE

Further studies are warranted to determine whether the present study design can play a role in testing auditory function in clinical infant populations.

Newborns discriminate novel from harmonic sounds: A study using magnetoencephalography

OBJECTIVE

We investigated whether newborns respond differently to novel and deviant sounds during quiet sleep.

METHODS

Twelve healthy neonates were presented with a three-stimulus oddball paradigm, consisting of frequent standard (76%), infrequent deviant (12%), and infrequent novel stimuli (12%). The standards and deviants were counterbalanced between the newborns and consisted of 500 and 750 Hz tones with two upper harmonics. The novel stimuli contained animal, human, and mechanical sounds. All stimuli had a duration of 300 ms and the stimulus onset asynchrony was 1s. Evoked magnetic responses during quiet sleep were recorded and averaged offline.

RESULTS

Two deflections peaking at 345 and 615 ms after stimulus onset were observed in the evoked responses of most of the newborns. The first deflection was larger to novel and deviant stimuli than to the standard and, furthermore, larger to novel than to deviant stimuli. The second deflection was larger to novel and deviant stimuli than to standards, but did not differ between the novels and deviants.

CONCLUSIONS

The two deflections found in the present study reflect different mechanisms of auditory change detection and discriminative processes.

SIGNIFICANCE

The early brain indicators of novelty detection may be crucial in assessing the normal and abnormal cortical function in newborns. Further, studying evoked magnetic fields to complex auditory stimulation in healthy newborns is needed for studying the newborns at-risk for cognitive or language problems.

Maturation of the cortical auditory evoked potential in infants and young children

The aim of this study was to evaluate the maturation of the cortical auditory evoked potential (CAEP) in humans. The participants in this experiment were 10 newborns (<7 days), 19 toddlers (13-41 months), 20 children (4-6 years) and 9 adults (18-45 years). CAEPs were obtained in response to low (400 Hz) and high (3000 Hz) tones and to the word token /baed/, all presented at 60 dB HL, at a rate of 0.22 Hz. Latency and amplitude measures were made for CAEP components P1, N1, P2 and N2 as a function of participant age, stimulus type and electrode montage. CAEP component latencies were relatively stable from birth to 6 years, but adults demonstrated significantly shorter latencies compared to infants and children. Components P1 and N2 decreased in amplitude, while components N1 and P2 increased in amplitude from birth to adulthood. Words evoked significantly larger CAEPs in newborns compared to responses evoked by tones, but in other age groups the effects of stimulus type on component amplitudes and latencies were less consistent. There was evidence of immature tonotopic organisation of the generators of N1 when responses from infants and young children were compared to those of adults. The scalp distribution of components N1 and P2 was clearly different in newborns and toddlers compared to children and adults. In the younger groups, both N1 and P2 were uniformly distributed across the scalp but in children and adults these components showed more focal distributions, with evidence of response laterality increasing with maturity. The results of the present study describe, for the first time, CAEPs recorded from multiple scalp electrodes, for tones and speech stimuli, in infants and children from birth to 6 years of age. Frequency-related differences in component amplitude were apparent at all ages reflecting development of tonotopic organisation of the CAEP neural generators.

Maturation of CAEP in infants and children: A review

This paper reviews our current understanding of the development of the obligatory cortical auditory evoked potential (CAEP) components P1, N1, P2, and N2. Firstly, the adult CAEP is briefly reviewed with respect to its morphology, neural generators and stimulus-dependence. Secondly, age-related changes occurring from the newborn period through childhood and adolescence are reviewed. The focus is on the maturation of CAEP morphology, changes in the scalp topography of the various components, changes in their amplitude and latency and in their stimulus-dependence. This review identifies periods of development in which we have only limited understanding of cortical auditory processing, as revealed by evoked potentials.

Avaliação auditiva central com BERA e P300 na Doença de Parkinson

Introdução: A Doença de Parkinson (DP) é um dos distúrbios do movimento mais encontrados na população idosa. Cursa com perda progressiva e irreversível de células da substância negra (locus niger) do mesencéfalo, o que resultará numa diminuição da produção de dopamina, levando à sintomatologia da DP. Objetivo: Averiguar a relevância de testes eletrofisiológicos, capazes de monitorar a integridade funcional das vias cerebrais, no diagnóstico e/ou prognóstico de pacientes com DP, uma vez que tais testes não-invasivos são de fácil aplicabilidade, rápidos e facilmente compreendidos por quem participa de sua aplicação. Forma de estudo: Prospectivo clínico randomizado. Material e Método: Grupo de 32 pacientes com diagnóstico prévio de DP, submetidos aos testes de potencial evocado BERA e P300. Pacientes de ambos os sexos, entre 44 e 85 anos, com tempo de doença variando de 8 meses a 21 anos de evolução. Resultados: os valores do BERA e do P300 encontrados em pacientes com DP não se mostraram diferentes dos limites de normalidade para a idade. Conclusão: Observou-se integridade das vias auditivas em pacientes portadores de DP. Uma vez que a latência do P300 aumenta de forma linear com a idade, a partir dos 45 anos, aceitando-se um aumento de 1 a 1,5ms por ano¹; observou-se integridade nas vias cerebrais que refletem a habilidade de performance cognitiva em pacientes portadores de DP sem comprometimento demencial exuberante.

Maturation of mismatch negativity in typically developing infants and preschool children

OBJECTIVE

1) To determine whether an adult-like mismatch negativity (MMN) can be reliably elicited in typically developing awake infants and preschool children, and if so 2) to examine whether maturational changes exist in MMN latencyand amplitude.

DESIGN

Two experiments were designed to elicit MMN using an "oddball" paradigm. In Experiment 1, a 1000-Hz tone served as the standard stimulus and a 1200-Hz tone as the deviant. In Experiment 2, a 1000-Hz standard stimulus and a 2000-Hz deviant were presented. Infants' ages ranged from 2 to 47 and 3 to 44 mo in Experiments 1 and 2, respectively.

RESULTS

In Experiment 1, a negativity was not elicited in the majority of the infants and preschoolers tested. In Experiment 2, a negativity was reliably elicited in the infants and preschoolers across all ages. A significant negative correlation was observed between age and latency, but not for age and amplitude for this negativity. This negativity was found to decrease at a rate of 1 msec/mo. Infants younger than 12 mo of age showed a significantly larger positivity to the deviant than to the standard between 150-300 and 200-300 msec in Experiments 1 and 2, respectively.

CONCLUSIONS

The discriminative processes indexed by MMN in response to frequency changes areimmature in infants and preschool children. Although there is convincing evidence that the negativity elicited in Experiment 2 is an immature MMN, the possibility that it may be an "obligatory effect" indexing recovery from refractoriness cannot be ruled out at this time. The results from these experiments suggest that the MMN component haslimited use as a clinical tool at this time for infants and young children.

Mismatch negativity (MMN) as a tool for investigating auditory discrimination and sensory memory in infants and children

For decades behavioral methods, such as the head-turning or sucking paradigms, have been the primary methods to investigate auditory discrimination, learning and the function of sensory memory in infancy and early childhood. During recent years, however, a new method for investigating these issues in children has emerged. This method makes use of the mismatch negativity (MMN), the brain's automatic change-detection response, which has been used intensively in both basic and clinical studies in adults for twenty years. This review demonstrates that, unlike many other components of event-related potentials, the MMN is developmentally quite stable and can be obtained even from pre-term infants. Further, MMN amplitude is only slightly smaller in infants than is usually reported in school-age children and it does not seem to differ much from that obtained in adults. MMN latency has been reported to be slightly longer in infants than in adults but reaches adult values by the early school-age years. Child MMN does not seem to be analogous to adult MMN, however. For example, contrary to the results of adult studies, a prominent MMN can be obtained from in all waking- and sleep states in infants. Moreover, MMN scalp distribution seems to be broader and more central in children than in adults.

Topography of auditory evoked long-latency potentials in normal children, with particular reference to the N1 component

Topographic maps of late auditory evoked potentials were obtained with the Brain Atlas III system in 34 healthy, normal hearing children aged 8-16 years. The stimulus was a 100 msec, 500 Hz tone burst, presented separately to the left and right ears, at 75 dB HL. The resulting auditory evoked potentials showed a prominent N1, after about 100 msec, and a topographic map with a corresponding fronto-lateral focus designated as the focus of N1 (FN1). Foci with varying positions and amplitudes were identified in 33 of 34 subjects after left ear stimulation and in 29 of 32 subjects after right ear stimulation. The topography showed a high degree of stability in most subjects, with the position of the negative "peak" of FN1 in front of the interaural line and with a dominance contralateral to the ear stimulated. There was a significant decrease in the latency of N1 with increasing age. FN1 tended to change position with age and some differences from adults were also observed. In conclusion, a distinct topographic pattern of the N1 component of the late auditory evoked potentials was seen in the majority of children. It remains to be established to what extent this method may be clinically useful for disclosing functional disturbances in the central auditory pathways.

Auditory event-related potentials in waking infants and adults: a developmental perspective

Auditory event-related potentials (AERPs) were recorded in waking 1 month olds, 3 month olds, 6 month olds and adults in order to study the morphology and development of the wave form in the waking subject. Previous data were generally obtained in sleeping or drowsy infants. The findings indicated that there were 3 quantitative changes in the AERP over the first 6 months of life in waking infants: an increase in the latency of peaks, an increase in peak amplitude, and a decrease in intersubject variability. Adult peak latencies were generally shorter than those for 3 month olds and 6 month olds. Further, latencies of earlier AERP peaks for 1 and 6 month olds, in the present study, were comparable to those reported in previous investigations with sleeping infants. However, latencies of later AERP peaks differed from those of previous reports and were closer to those reported for waking adults. With respect to the amplitude, the 6 month olds, in general, had the highest amplitudes, the 1 month olds the lowest, and the 3 month olds and adults fell in between the two groups. Some differences were present between early and late components. The findings of this study are significant in that the AERPs were quantitatively different from those reported in earlier work with sleeping or drowsy infants. If cognitive and perceptual development is to be studied, it is necessary to obtain data on waking subjects. The data presented in this report are consistent with behavioral studies of biobehavioral shifts that are associated with changes in responsivity of the organism to stimuli during the first 6 months of life.

Auditory brain-stem evoked potentials to clicks at different presentation rates: estimating maturation of pre-term and full-term neonates

Auditory brain-stem evoked potentials ABEPs were recorded from 57 neonates ranging in gestational age between 27 and 43 weeks. Averages and standard deviations of I, III and V peak latencies, I-V, I-III and III-V inter-peak latency differences (IPLDs), for 10/sec and 55/sec clicks were calculated for each age group. An additional measure, the net effect of increasing stimulus rate (ISR), was calculated by subtracting 10/sec measures from their 55/sec counterparts. Correlations between ABEP measures and subject age were determined. The results of this study demonstrate a significant correlation between gestational age and electrophysiological measures of peripheral, as well as central, conduction: an inverse correlation between age and peak latencies as well as IPLDs. The slope of this correlation was steeper for the higher stimulus rate. The slope of 55/sec measures vs. age was the sum of the respective slopes of 10/sec measures and of ISR. The maturation of 10/sec measures may reflect white matter development, while ISR changes with gestational age represent maturation of synaptic efficacy. Thus, the maturation of 55/sec measures reflect the combined maturation of nerve conduction velocity and synaptic efficacy along the neonatal auditory nerve and brain-stem. This differential evaluation may enable more accurate determination of developmental age of neonates, with respect to total maturation as well as its constituents.

Differential maturation of cortical auditory evoked potentials to speech sounds in normal fullterm and very low-birthweight infants

Cortical auditory evoked potentials (AEP) to the consonant-vowel syllables/da/and/ta/and 800Hz tone were recorded at 40 weeks post-conceptional age and at one, two and three months after term in normal fullterm and very low-birthweight infants. As a group, the very low-birthweight infants exhibited significantly less mature AEPs to consonant-vowel syllables than the normal-birthweight infants at 40 weeks post-conceptional age. Consistent but statistically non-significant differences also were found for tones at 40 weeks post-conceptional age, and for all stimuli at one and two months after term. By three months, all the infants exhibited mature AEP morphology and topography.

The evolution of visual and auditory evoked potentials in infants with perinatal disorder

The evolutionary changes of evoked potentials (EPs) were studied from the neonatal period up to 1 year of age in 41 infants with various perinatal disorders. Abnormal EPs in the first week of life recovered quickly. In infants with normal outcome, abnormal EPs became normal within a month. In infants with cerebral palsy (CP) or mental retardation (MR), EPs recovered within 2-3 months of age. Infants with more severe neurological damage showed abnormal EPs even beyond 6 months of age. Abnormal EPs beyond 2 weeks of age indicated poor prognosis. As for the wave form of EPs, absent responses or abnormal wave form reflected more severe brain dysfunction. AEPs tended to show more profound abnormalities than VEP. However, some infants with absent AEP in the first week of life had a favorable prognosis. AEPs seemed to be more easily affected by brain dysfunction.

Auditory evoked potential development in early childhood: a longitudinal study

Serial recordings of auditory evoked potentials (AEPs) to clicks were obtained using a vertex-mastoid derivation from 16 normal children during sleep over an age span from near birth to age 3. The AEP components studied were: N0 (38 +/- 10 msec), P1 (79 +/- 24 msec), N1 (109 +/- 39 msec), P2 (186 +/- 35 msec), N2 (409 +/- 97 msec), P3A (554 +/- 116 msec), P3B (757 +/- 121 msec) and P3 (728 +/- 128 msec). Amplitudes and latencies of the components were calculated and regressions of the measures on age were computed for the group as a whole, for each subject and for subsets of the data based on sleep stage, sex, order of stimulus presentation and a rearing/race factor. For the group as a whole the latencies of P1, P2, P3, and P3B decreased with age. The amplitudes of P1N1 and the N2P3 waves increased with age. Most change occurred during the first year of life. In general, the changes with age were also found to hold across all of the factors examined, although individuals varied widely in the degree to which they conformed to the trends found for the data as a whole. The amount contributed by each of the factors mentioned above to the total variance was estimated. The proportions varied for different EP components but, in general, age, sleep state, and subject factors other than rearing/race and sex accounted for most variance. One half to 5/6 of the unexplained variance in AEP latencies and amplitudes (i.e., that not due to age, sleep state, etc.) occurred across rather than within subjects. For both the group as a whole and for individual children, P2 and N2 latencies were found to exhibit the greatest stability across time. The results of the longitudinal study reported here were in good agreement with those of a previous study from this laboratory which utilized a cross-sectional design.

Age-related variations in evoked potentials to auditory stimuli in normal human subjects

Auditory evoked potentials were recorded from 47 subjects ranging in age from 6 to 76 years in order to assess the effects of maturation and aging on the evoked (N1 and P2) and event-related (N2 and P3) components. Because of clear differences in the effects of age on the event-related components between children (less than 15 years of age) and adults the subjects were divided into two populations for analysis. For adults there was a systematic increase in the latency and decrease in amplitude of each component with age. Also the rate of the age-related increase in latency was proportional to the latency of the component. The scalp distributions of both the stimulus-evoked and event-related components were found to vary with age yielding a more nearly equipotential distribution for older subjects. For children the latencies of the event-related components decreased with age. The stimulus-evoked components had latencies which were not significantly different from those predicted from the adult data. In contrast to the adult data, age affected the scalp distributions of the stimulus-evoked components differently than the event-related components. These results suggest an aging process is relfected in the auditory evoked potential which is not the simple inverse of maturational processes.

Postnatal development of human brainstem potentials during the first year of life

Average brainstem potentials evoked by auditory stimuli were recorded from the scalp's surface of human newborns and infants, 6 weeks, 3 months, 6 months and 1 year of age as well as from normal adults. The auditory processes related to peripheral transmission (PT) and central transmission (CT) were shown to mature at differential rates during the first year of life. By the 6th week PT had reached the adult latency. In contrast, CT through the brainstem did not match that of the adult until approximately 1 year of age. In addition, the waveform of the brainstem evoked potential (BEP) displayed an independent time course for development. The adult configuration replaced the infantile response by 3--6 months. Despite considerable inter-subject variability in the BEP amplitude during the neonatal period, a general wave-form pattern could easily be delineated. Preliminary results revealed the BEP to be quite resistant to habituation following continuous stimulus presentation. Longitudinal follow-ups on several babies paralleled the transverse data.

Auditory evoked potentials during sleep in normal children from ten days to three years of age

Auditory evoked potentials (AEPs) to clicks of moderate intensity were studied in 130 normal sleeping children from 10 days to 3 years of age. Latencies of the principal response components were found to decrease with log age, i.e., change was most rapid during the first year of life. From 15 days of age to 3 years, mean latencies decreased as follows: P2 from 230 to 150, N2 from 535 to 320 and P3 from 785 to 625 msec. Variance was quite high, especially at younger ages. The fact that decreases in the latencies of the various components proceeded at different rates suggest that the components reflect quasi-independent neural substrates. The components of shortest latency displayed the weakest relationship to age. Findings with respect to latency for the subset of data obtained during stage 2 sleep were similar to those for the total population which contained responses recorded during several sleep stages. The amplitude of AEP components increased with age with the exception of N1P2 which decreased. Observations with regard to amplitude held both for the overall data recorded during several sleep stages and stage 2 data for components N0P1, N1P2 and N2P3. The amplitude trends for P1N1 and P2N2 were, however, not significant for the stage 2 subset. The maturation of the morphology of the AEP was characterized by a relative increase in the prominence of long latency components. The most striking change was the development of P3. High amplitude, V shaped P3 waves were also associated with stage 3-4 sleep. The changes which were delineated by this study for infancy and early childhood appear to be continuations of developmental trends reported for premature infants and neonates. AEPs are a reliable elicited measure which correlate well with maturation. They, therefore, can be a useful tool both in the study of central nervous system development and in the diagnosis of sensory and neurologic abnormalities.

Early averaged electroencephalic responses to clicks in neonates

The early (approximately 8–50 msec latency) averaged electroencephalic responses (AER) to 55 dB HL clicks were elicited from ten normal newborns 36 to 72 hours after birth. Early components were observed in all ten babies with 512 clicks presented at 4.5/sec and 9.0/sec. Mean peak latencies in msec were: Po — 11, Na — 17, Pa — 28, Nb — 35, and Pb — 51. The neonates' early component waveforms closely resemble those of adults. The latency and waveform stability of the early components in neonates and adults support the belief in the primary auditory (lemniscal) system as the mediator of these responses. Furthermore, the repeatability of the early components of the AER makes them more reliable response indices than the late components (approximately 50–400 msec) for audiometry with neonates.