Auditory Maturation Research Articles

Effects of prematurity on language acquisition and auditory maturation: a systematic review.

To verify which damages prematurity causes to hearing and language. We used the decriptors language/linguagem, hearing/audição, prematurity/prematuridade in databases LILACS, MEDLINE, Cochrane Library and Scielo. randomized controlled trials, non-randomized intervention studies and descriptive studies (cross-sectional, cohort, case-control projects). The articles were assessed independently by two authors according to the selection criteria. Twenty-six studies were selected, of which seven were published in Brazil and 19 in international literature. Nineteen studies comparing full-term and preterm infants. Two of the studies made comparisons between premature infants small for gestational age and appropriate for gestational age. In four studies, the sample consisted of children with extreme prematurity, while other studies have been conducted in children with severe and moderate prematurity. To assess hearing, these studies used otoacoustic emissions, brainstem evoked potentials, tympanometry, auditory steady-state response and visual reinforcement audiometry. For language assessment, most of the articles used the Bayley Scale of Infant and Toddler Development. Most studies reviewed observed that prematurity is directly or indirectly related to the acquisition of auditory and language abilities early in life. Thus, it could be seen that prematurity, as well as aspects related to it (gestational age, low weight at birth and complications at birth), affect maturation of the central auditory pathway and may cause negative effects on language acquisition.

Age-Related Maturation of Wave V Latency of Auditory Brainstem Response in Children.

Background and ObjectivesAuditory brainstem response (ABR) is a noninvasive measurement of a stimulus-locked, synchronous electrical event. ABR provides information concerning the functional integrity of brainstem nuclei. Age is a key factor in the interpretation of ABR peak latency among different age groups. Progressively with time it follows a "maturation pattern" during which latencies decrease. Wave V is very prominent and reliable for detection of threshold in children. The present study was performed to see the effect of age related auditory maturation on ABR wave V latency in children.Subjects and MethodsThe study involved 80 subjects ranging in age from birth to 12 years. The subjects were divided equally into eight age groups. ABR were elicited by an acoustic click stimuli, brainstem responses collected through electrode and recorded at the same time. Latency of wave V was acknowledged.ResultsWave V latency decreased rapidly in early childhood, became slower after 3 years of age and completely matured by 12 years of age. There was no significant difference in latency of wave V between the ears with age.ConclusionsThere is a distinct maturation pattern of wave V latency in ABR for both ears. ABR is a reliable test to assess the functional maturation of wave V in children.

76. Maturational changes of the auditory system in normal preschool children assessed by brainstem auditory evoked potentials (BAEPs)

Introduction Absolute latencies and inter peak latencies of wave brainstem auditory evoked potentials (BAEP) changes with the maturation of the auditory pathway, which is reached between 18 and 36 months old. Objective To describe the maturation of BAEPs in healthy preschool children. Methods Cross-sectional study. A sample of 102 preschool children were studied with adequate neurodevelopmental, age distribution (12–23 months, 24–35 months, 36–47 months, 48–59 month and 60–71 months). The stimulation parameters were: rarefaction, click, 80 dBnHL intensity, frequency 11.1 Hz and average of 2000 stimuli. We evaluated absolute latencies for I, III and V waves and interpeak latencies I–III, III–V and I–V expressed in milliseconds (ms) and hearing threshold expressed in decibels (dB). Results 102 studies 68% men 32% women. The wider distribution of the sample was in the 3–4 groups ( n = 46). The absolute latencies and interpeak latencies were the same for all age groups. The hearing threshold was normal in 100% of cases. Conclusions The auditory pathway maturity is reached at 2 years of age; it is necessary to increase the sample size to corroborate this premise. Significance The reference values of BAEPs reported in adults can be used from 2 years old.

Longitudinal Comparison of Auditory Steady-State Evoked Potentials in Preterm and Term Infants: The Maturation Process.

Introduction Preterm neonates are at risk of changes in their auditory system development, which explains the need for auditory monitoring of this population. The Auditory Steady-State Response (ASSR) is an objective method that allows obtaining the electrophysiological thresholds with greater applicability in neonatal and pediatric population. Objective The purpose of this study is to compare the ASSR thresholds in preterm and term infants evaluated during two stages. Method The study included 63 normal hearing neonates: 33 preterm and 30 term. They underwent assessment of ASSR in both ears simultaneously through insert phones in the frequencies of 500 to 4000Hz with the amplitude modulated from 77 to 103Hz. We presented the intensity at a decreasing level to detect the minimum level of responses. At 18 months, 26 of 33 preterm infants returned for the new assessment for ASSR and were compared with 30 full-term infants. We compared between groups according to gestational age. Results Electrophysiological thresholds were higher in preterm than in full-term neonates ( p < 0.05) at the first testing. There were no significant differences between ears and gender. At 18 months, there was no difference between groups ( p > 0.05) in all the variables described. Conclusion In the first evaluation preterm had higher thresholds in ASSR. There was no difference at 18 months of age, showing the auditory maturation of preterm infants throughout their development.

Neuroplasticity with cochlear implants: Underlying neuronal mechanisms

Chronic cochlear implant (CI) stimulation in congenitally deaf cats (CDCs) leads to cortical maturation matching imaging data from humans (Kral and Sharma, 2012, TINS). One possible measure of auditory plasticity is the reorganization of aural preference following monaural CIs (Kral et al., 2013, Brain), showing a sensitive period of <4.2 months in cats. A substantial reduction of binaural information following developmental unilateral hearing was found in cortical neurons (Kral et al., 2015, Audiol Neurootol). Consequently, auditory maturation requires experience. Additional to reduced synaptic plasticity, loss of acuity in feature representation, deficits in integrative function of the cortical column and deficits in corticocortical, particularly top-down, interactions, close the sensitive periods (Kral 2013, Neuroscience). Cross-modal plasticity recruits auditory resources for non-auditory tasks. Despite of cross-modal reorganization in some auditory areas the extend of the underlying reorganization of corticortical connections (Barone et al., 2013, PLoS One) indicates that this only moderately limits auditory processing capacity. Electrophysiological recordings in the dorsal auditory cortex of CDCs demonstrate that the cross-modally reorganized secondary auditory areas maintain a predominance of dormant auditory inputs additional to moderate cross-modal reorganization. [Supported by Deutsche Forschungsgemeinschaft (Cluster of Excellence Hearing4all).]

THE STUDY OF MATURATION OF THE AUDITORY ANALYZER RABBIT ACCORDING DISTORTION-PRODUCT OTOACOUSTIC EMISSIONS

In our chronic experiment to register changes of acoustic response of Distortion-Product Otoacoustic Emissions (DPOAE) of intact rabbits in postnatal ontogenesis for the purpose of getting normative data which can be used for studying impact of pathological factors on auditory function and maturation of activity of outer hair cell in ontogenesis. Study of otoacoustic emissions used mature chinchilla rabbits with a 19 day life of up to 3 months. In the course of ripening were obtained functional activity of outer hair cells of the cochlea. normative data obtained allow us to study using a rabbit model, the pathological effects of agents on the maturation of the outer hair cells of the cochlea in the experiment.

Central auditory development in children with hearing impairment: Clinical relevance of the P1 CAEP biomarker in children with multiple disabilities

Objective: We review the development and plasticity of the central auditory pathways in infants and children with hearing loss who are fitted with cochlear implants (CIs). Secondly, we describe case studies demonstrating the clinical utility of the P1 central auditory evoked potential (CAEP) for evaluating cortical auditory maturation in the rapidly increasing number of cochlear-implanted children who have multiple disabilities. Study design: Children who receive CIs provide a platform to examine the trajectories of deprivation-induced and experience-dependent plasticity in the central auditory system. We review the evidence for, and time-limits of, sensitive periods for cortical auditory maturation framing an optimal period for cochlear implantation. Finally, we evaluate the use of the P1 biomarker as an objective assessment tool in the special case of children with multiple disabilities. Results: The P1 response was useful in assessing central auditory maturation in patients with CHARGE association, ANSD, and Pallister-Killian syndrome concomitant with hearing loss. Conclusion: The presence of coexisting disabilities in addition to hearing loss poses unique challenges regarding both pre-intervention evaluation and post-intervention rehabilitation for children with multiple disabilities. When combined with a standard audiological test battery, the P1 CAEP biomarker has a useful role in objectively evaluating the maturation of central auditory pathways to determine the effectiveness of various intervention strategies in hearing-impaired children with multiple disabilities.

Central auditory maturation and behavioral outcome in children with auditory neuropathy spectrum disorder who use cochlear implants

Objective: We examined cortical auditory development and behavioral outcomes in children with ANSD fitted with cochlear implants (CI). Design: Cortical maturation, measured by P1 cortical auditory evoked potential (CAEP) latency, was regressed against scores on the infant toddler meaningful auditory integration scale (IT-MAIS). Implantation age was also considered in relation to CAEP findings. Study sample: Cross-sectional and longitudinal samples of 24 and 11 children, respectively, with ANSD fitted with CIs. Results: P1 CAEP responses were present in all children after implantation, though previous findings suggest that only 50–75% of ANSD children with hearing aids show CAEP responses. P1 CAEP latency was significantly correlated with participants’ IT-MAIS scores. Furthermore, more children implanted before age two years showed normal P1 latencies, while those implanted later mainly showed delayed latencies. Longitudinal analysis revealed that most children showed normal or improved cortical maturation after implantation. Conclusion: Cochlear implantation resulted in measureable cortical auditory development for all children with ANSD. Children fitted with CIs under age two years were more likely to show age-appropriate CAEP responses within six months after implantation, suggesting a possible sensitive period for cortical auditory development in ANSD. That CAEP responses were correlated with behavioral outcome highlights their clinical decision-making utility.

Auditory maturation in premature infants

To describe spontaneous hearing improvement in the first years of life of a number of preterm neonates relative to cochlear implant candidacy. Retrospective case study. Hearing levels of 14 preterm neonates (mean gestational age at birth = 29 weeks) referred after newborn hearing screening were evaluated. Initial hearing thresholds ranged from 40 to 105 dBHL (mean = 85 dBHL). Hearing level improved to normal levels for four neonates and to moderate levels for five, whereas for five neonates, no improvement in hearing thresholds was observed and cochlear implantation was recommended. Three of the four neonates in whom the hearing improved to normal levels were born prior to 28 weeks gestational age. Hearing improvement was mainly observed prior to a gestational age of 80 weeks. Delayed maturation of an immature auditory pathway might be an important reason for referral after newborn hearing screening in premature infants. Caution is advised regarding early cochlear implantation in preterm born infants. Audiological follow-ups until at least 80 weeks gestational age are therefore recommended.

Embryonic assembly of auditory circuits: spiral ganglion and brainstem

During early development, peripheral sensory systems generate physiological activity prior to exposure to normal environmental stimuli. This activity is thought to facilitate maturation of these neurons and their connections, perhaps even promoting efficacy or modifying downstream circuitry. In the mammalian auditory system, initial connections form at embryonic ages, but the functional characteristics of these early neural connections have not been assayed. We investigated processes of embryonic auditory development using a whole-head slice preparation that preserved connectivity between peripheral and brainstem stations of the auditory pathway. Transgenic mice expressing fluorescent protein provided observation of spiral ganglion and cochlear nucleus neurons to facilitate targeted electrophysiological recording. Here we demonstrate an apparent peripheral-to-central order for circuit maturation. Spiral ganglion cells acquire action potential-generating capacity at embryonic day 14 (E14), the earliest age tested, and action potential waveforms begin to mature in advance of comparable states for neurons of the ventral cochlear nucleus (VCN) and medial nucleus of the trapezoid body (MNTB). In accordance, auditory nerve synapses in the VCN are functional at E15, prior to VCN connectivity with the MNTB, which occurs at least 1 day later. Spiral ganglion neurons exhibit spontaneous activity at least by E14 and are able to drive third-order auditory brainstem neurons by E17. This activity precedes cochlear-generated wave activity by 4 days and ear canal opening by at least 2 weeks. Together, these findings reveal a previously unknown initial developmental phase for auditory maturation, and further implicate the spiral ganglion as a potential controlling centre in this process.

Auditory maturity and hearing performance in inner ear malformations: a histological and electrical stimulation approach

The objective of this study was to assess the auditory performance of the neural structures in response to controlled electrical stimulation period. A prospective cohort study focused on the intracochlear electrical stimulation parameters and hearing performance of patients suffering different cochlear malformations who were treated by cochlear implants constituted the study design. The study sample constituted 16 patients, suffering profound prelingual hearing impairment, diagnosed on the basis of radiological criteria as having an inner ear malformation, and who underwent cochlear implantation and were followed for 24 months. Patients with common cavities, characterized by fewer nerve structures involved, less epithelial penetration, and deficient cochlear tonotopy distribution showed have higher thresholds and electrical charges than patients with cochlear hypoplasia, who in turn have higher thresholds than patients with minor malformations (p < 0.05). Furthermore, word perception was severely compromised in patients with a common cavity malformation and was also poor in patients with cochlear hypoplasia, who were unable to discriminate more than 50% of the words and relied on visual cues as a necessary aid to communication. Better results were reached by minor malformed inner ears. To conclude, the number of nerve structures involved, epithelial penetration and deficient cochlear tonotopy are responsible of inner ear functionality.

Auditory development between 7 and 11 years: an event-related potential (ERP) study.

Background There is considerable uncertainty about the time-course of central auditory maturation. On some indices, children appear to have adult-like competence by school age, whereas for other measures development follows a protracted course.Methodology We studied auditory development using auditory event-related potentials (ERPs) elicited by tones in 105 children on two occasions two years apart. Just over half of the children were 7 years initially and 9 years at follow-up, whereas the remainder were 9 years initially and 11 years at follow-up. We used conventional analysis of peaks in the auditory ERP, independent component analysis, and time-frequency analysis.Principal Findings We demonstrated maturational changes in the auditory ERP between 7 and 11 years, both using conventional peak measurements, and time-frequency analysis. The developmental trajectory was different for temporal vs. fronto-central electrode sites. Temporal electrode sites showed strong lateralisation of responses and no increase of low-frequency phase-resetting with age, whereas responses recorded from fronto-central electrode sites were not lateralised and showed progressive change with age. Fronto-central vs. temporal electrode sites also mapped onto independent components with differently oriented dipole sources in auditory cortex. A global measure of waveform shape proved to be the most effective method for distinguishing age bands.Conclusions/SignificanceThe results supported the idea that different cortical regions mature at different rates. The ICC measure is proposed as the best measure of ‘auditory ERP age’.

Clinical Application of the P1 Cortical Auditory Evoked Potential Biomarker in Children with Sensorineural Hearing Loss and Auditory Neuropathy Spectrum Disorder

The P1 component of the cortical auditory evoked potential (CAEP) shows clearly documented age-related decreases in latency and changes in morphology in normal hearing children, providing a biomarker for development of the auditory cortical pathways in humans. In hearing-impaired children, auditory deprivation may affect the normal age-related changes in central auditory maturation. Appropriate early intervention with amplification and/or electrical stimulation can provide the necessary stimulation needed to drive progress in central auditory maturation and auditory skill development, however objective measures are needed to evaluate the effectiveness of these treatments in infants and young children. We describe three pediatric cases, where we explored the clinical utility of the P1 as an objective biomarker of auditory cortical development after early intervention. We assessed development of P1 CAEP latency and morphology in two children with sensorineural hearing loss (SNHL) who received intervention with hearing aids (case 1) and cochlear implants (case 2) and a child with Auditory Neuropathy Spectrum Disorder (ANSD) (case 3). Overall, we find that the P1 CAEP serves as useful tool for assessing the effectiveness of early intervention treatment and clinical management of pediatric hearing- impaired patients.

Cortical maturation and behavioral outcomes in children with auditory neuropathy spectrum disorder

Objective. Auditory neuropathy spectrum disorder (ANSD) affects approximately 10% of patients with sensorineural hearing loss. While many studies report abnormalities at the level of the cochlea, auditory nerve, and brainstem in children with ANSD, much less is known about their cortical development. We examined central auditory maturation in 21 children with ANSD. Design. Morphology, latency and amplitude of the P1 cortical auditory evoked potential (CAEP) were used to assess auditory cortical maturation. Children's scores on a measure of auditory skill development (IT-MAIS) were correlated with CAEPs. Study Sample. Participants were 21 children with ANSD. All were hearing aid users. Result. Children with ANSD exhibited differences in central auditory maturation. Overall, two-thirds of children revealed present P1 CAEP responses. Of these, just over one third (38%) showed normal P1 response morphology, latency and amplitude, while another third (33%) showed delayed P1 response latencies and significantly smaller amplitudes. The remaining children (29%) revealed abnormal or absent P1 responses. Overall, P1 responses were significantly correlated with auditory skill development. Conclusion: Our results suggest that P1 CAEP responses may be: (i) A useful indicator of the extent to which neural dys-synchrony disrupts cortical development, (ii) A good predictor of behavioral outcome in children with ANSD.SumarioObjetivo: El espectro de desórdenes de la neuropatía auditiva (ANSD) afecta a casi 10% de los pacientes con hipoacusia sensorineural. Mientras que muchos estudios reportan anormalidades al nivel de la cóclea, el nervio auditivo y el tallo cerebral en los niños con ANSD, se sabe mucho menos sobre su desarrollo cortical. Examinamos la maduración auditiva central en 21 niños con ANSD. Diseño: Se utilizó la morfología, la latencia y la amplitud de la P1 de los potenciales corticales auditivos evocados (CAEO) para evaluar la maduración de la audición cortical. Se correlacionaron las calificaciones de los niños en la prueba de desarrollo de habilidades auditivas (IT-MAIS) con los CAEPs. Muestra: Participaron 21 niños con ANSD, todos usuarios de auxiliares auditivos. Resultados: Los niños con ANSD mostraron diferencias en la maduración central auditiva. En general, dos tercios de los niños mostraron respuestas de P1 en los CAEP. De ellos, aproximadamente un tercio (38%) mostró una morfología normal de la P1, de la latencia y de la amplitud, mientras que otro tercio (33%) mostró una latencia retrasada de la respuesta P1 y una amplitud significativamente menor. El resto de los niños (29%) mostró una respuesta anormal o ausente de la P1. En general las respuestas se correlacionaron significativamente con las habilidades auditivas desarrolladas. Conclusiones: Nuestros resultados sugieren que la P1 de los CAEP pueden ser: (i) un indicador útil de la medida en la que la dis-sincronía auditiva altera el desarrollo cortical y (ii) es un buen vaticinador del resultado conductual de los niños con ANSD.

Incidence and clinical value of prolonged I–V interval in NICU infants after failing neonatal hearing screening

Infants admitted to neonatal intensive care units (NICUs) have a higher incidence of perinatal complications and delayed maturational processes. Parameters of the auditory brainstem response (ABR) were analyzed to study the prevalence of delayed auditory maturation or neural pathology. The prevalence of prolonged I–V interval as a measure of delayed maturation and the correlation with ABR thresholds were investigated. All infants admitted to the NICU Sophia Children’s Hospital between 2004 and 2009 who had been referred for ABR measurement after failing neonatal hearing screening with automated auditory brainstem response (AABR) were included. The ABR parameters were retrospectively analyzed. Between 2004 and 2009, 103 infants were included: 46 girls and 57 boys. In 58.3% (60 infants) of our population, the I–V interval was recordable in at least one ear at first diagnostic ABR measurement. In 4.9%, the I–V interval was severely prolonged. The median ABR threshold of infants with a normal or mildly prolonged I–V interval was 50 dB. The median ABR threshold of infants with a severely prolonged I–V interval was 30 dB. In conclusion, in case both peak I and V were measurable, we found only a limited (4.9%) incidence of severely prolonged I–V interval (≥0.8 ms) in this high-risk NICU population. A mild delay in maturation is a more probable explanation than major audiologic or neural pathology, as ABR thresholds were near normal in these infants.

Electrically Evoked Auditory Brainstem Responses in Children with Sequential Bilateral Cochlear Implants

OBJECTIVE: To examine the effect of sequential bilateral cochlear implantation on auditory brainstem maturation and the effect of age in receiving the second implant (CI2). STUDY DESIGN: Prospective cohort study. SETTING: Tertiary academic referral center. PATIENTS: Thirty prelingually deaf children, who received their first implant (CI1) at a mean age of 1.8 year and their CI2 at a mean age of 5.3 years. INTERVENTION: Sequential bilateral cochlear implantation. MAIN OUTCOME MEASURE: Electrically evoked auditory brainstem responses on the 2 implant sides were measured intraoperatively and postoperatively after 6, 12, and 24 months of bilateral implant use. RESULTS: Electrically evoked auditory brainstem response latencies on the 2 implants were compared within subjects over time. Wave III did not show any significant differences between the 2 sides, whereas Wave V was initially prolonged on the CI2 side compared with the CI1 side. Although still apparent, this interaural latency difference of Wave V was no longer significant after 12 and 24 months. Interwave interval III to V latencies remained significantly prolonged on the CI2 side. Age in receiving the CI2 did not account for the individual differences in latencies for all waveforms. CONCLUSION: The present data suggest that auditory brainstem maturation will occur after a relatively long period of unilateral deafness irrespective of the age in receiving the CI2. Because some abnormalities were still seen at the upper part of the brainstem, our results indicate that the CI2 side has not caught up with the CI1 side. Nevertheless, within our follow-up time, interaural (interwave) latencies decrease significantly, and longer-term data might reveal that the CI2 eventually will catch up with the CI1 side.

Independent Component Analysis for Robust Assessment of Auditory System Maturation in Children with Cochlear Implants

The long latency auditory evoked potential (LLAEP) has been used for tracking changes in latency and morphology of the P1 peak in order to evaluate the maturation of the auditory system in children with cochlear implants (CIs). Cochlear implants can induce an artefact in the recordings when sounds are presented, which makes the analysis of LLAEPs much harder. Independent component analysis (ICA) has been used to remove this artefact. In this paper we apply a procedure based on ICA to reduce the CI artefact, to detect the LLAEPs and to use the changes in the spatial projections of their independent components (ICs) for a robust evaluation of the maturation of the auditory system in children with CIs.

A new concern—in utero iron status

Clinicians caring for preterm infants routinely evaluate the hematocrit/hemoglobin status at birth, track hematocrit/hemoglobin with postnatal age, transfuse as necessary, and supplement with oral iron. Questions remain about how much transfusion is “necessary” and when and how much iron to supplement. In this issue of The Journal, Amin et al have added a new wrinkle to concerns about iron status. They used cord blood ferritin measurements to identify fetal iron status of infants born preterm. Of 80 infants born between 27 and 33 weeks gestation, 44% had latent iron deficiency, which correlated with abnormal auditory neural maturation – a window to brain maturation. Iron deficiency is well known to be a modulator of brain development, and some prenatal conditions (maternal iron deficiency, maternal diabetes, maternal smoking, and pregnancy-induced hypertension) are linked to fetal iron deficits at term. This paper now identifies a new concern – latent iron deficiency in preterms at birth. Should this deficiency as measured by blood ferritin levels be quickly corrected after birth? Most preterm infants do not end up with hearing deficits as children, but the abnormal auditory maturation may simply be an indicator of more generalized abnormalities in brain maturation. Clinicians caring for preterm infants routinely evaluate the hematocrit/hemoglobin status at birth, track hematocrit/hemoglobin with postnatal age, transfuse as necessary, and supplement with oral iron. Questions remain about how much transfusion is “necessary” and when and how much iron to supplement. In this issue of The Journal, Amin et al have added a new wrinkle to concerns about iron status. They used cord blood ferritin measurements to identify fetal iron status of infants born preterm. Of 80 infants born between 27 and 33 weeks gestation, 44% had latent iron deficiency, which correlated with abnormal auditory neural maturation – a window to brain maturation. Iron deficiency is well known to be a modulator of brain development, and some prenatal conditions (maternal iron deficiency, maternal diabetes, maternal smoking, and pregnancy-induced hypertension) are linked to fetal iron deficits at term. This paper now identifies a new concern – latent iron deficiency in preterms at birth. Should this deficiency as measured by blood ferritin levels be quickly corrected after birth? Most preterm infants do not end up with hearing deficits as children, but the abnormal auditory maturation may simply be an indicator of more generalized abnormalities in brain maturation. In Utero Iron Status and Auditory Neural Maturation in Premature Infants as Evaluated by Auditory Brainstem ResponseThe Journal of PediatricsVol. 156Issue 3PreviewTo determine whether cord ferritin (CF) concentration, an index of in utero iron status, is associated with auditory neural maturation in premature infants. Full-Text PDF

Development of Auditory Phase-Locked Activity for Music Sounds

The auditory cortex undergoes functional and anatomical development that reflects specialization for learned sounds. In humans, auditory maturation is evident in transient auditory-evoked potentials (AEPs) elicited by speech or music. However, neural oscillations at specific frequencies are also known to play an important role in perceptual processing. We hypothesized that, if oscillatory activity in different frequency bands reflects different aspects of sound processing, the development of phase-locking to stimulus attributes at these frequencies may have different trajectories. We examined the development of phase-locking of oscillatory responses to music sounds and to pure tones matched to the fundamental frequency of the music sounds. Phase-locking for theta (4-8 Hz), alpha (8-14 Hz), lower-to-mid beta (14-25 Hz), and upper-beta and gamma (25-70 Hz) bands strengthened with age. Phase-locking in the upper-beta and gamma range matured later than in lower frequencies and was stronger for music sounds than for pure tones, likely reflecting the maturation of neural networks that code spectral complexity. Phase-locking for theta, alpha, and lower-to-mid beta was sensitive to temporal onset (rise time) sound characteristics. The data were also consistent with phase-locked oscillatory effects of acoustic (spectrotemporal) complexity and timbre familiarity. Future studies are called for to evaluate developmental trajectories for oscillatory activity, using stimuli selected to address hypotheses related to familiarity and spectral and temporal encoding suggested by the current findings.

Development of auditory phase-locked activity for music sounds.

The auditory cortex undergoes anatomical and functional development that reflects specialization for learned sounds. Auditory maturation is evident in the transient auditory evoked potentials (AEPs) and auditory phase-locked oscillatory activity. Development of AEPs and the phase-locking strength of oscillatory auditory responses to piano, violin, and pure tones were examined. The hypothesis was that if oscillatory activity in different frequency bands reflects different aspects of sound processing, then the development of phase-locking at these frequencies will have different maturational trajectories. Phase-locking for theta (4–8 Hz), alpha (8–14 Hz), lower-to-mid-beta (14–25 Hz), and upper beta and gamma (25–70 Hz) bands strengthened with age and was stronger for musical than pure tones. The phase-locking increase for gamma and upper beta bands mainly reflected the maturation of the spectral representations for sounds. In contrast, increase in phase-locking for theta, alpha, and lower-to-mid-beta was mainly attributed to sensitivity to sound temporal onset rise time. Frequency-specific phase-locking provides a tool to assess auditory development for spectral and temporal aspects of naturalistic complex sounds. [This research was supported by grants from the Canadian Institutes of Health Research and the National Institutes of Health, National Institute on Deafness and other Communication Disorders.]