Garrett Cardon

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

Abstract 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. Childrens 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. Sumario Objetivo: 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.

Developmental and cross-modal plasticity in deafness: Evidence from the P1 and N1 event related potentials in cochlear implanted children

Cortical development is dependent on extrinsic stimulation. As such, sensory deprivation, as in congenital deafness, can dramatically alter functional connectivity and growth in the auditory system. Cochlear implants ameliorate deprivation-induced delays in maturation by directly stimulating the central nervous system, and thereby restoring auditory input. The scenario in which hearing is lost due to deafness and then reestablished via a cochlear implant provides a window into the development of the central auditory system. Converging evidence from electrophysiologic and brain imaging studies of deaf animals and children fitted with cochlear implants has allowed us to elucidate the details of the time course for auditory cortical maturation under conditions of deprivation. Here, we review how the P1 cortical auditory evoked potential (CAEP) provides useful insight into sensitive period cut-offs for development of the primary auditory cortex in deaf children fitted with cochlear implants. Additionally, we present new data on similar sensitive period dynamics in higher-order auditory cortices, as measured by the N1 CAEP in cochlear implant recipients. Furthermore, cortical re-organization, secondary to sensory deprivation, may take the form of compensatory cross-modal plasticity. We provide new case-study evidence that cross-modal re-organization, in which intact sensory modalities (i.e., vision and somatosensation) recruit cortical regions associated with deficient sensory modalities (i.e., auditory) in cochlear implanted children may influence their behavioral outcomes with the implant. Improvements in our understanding of developmental neuroplasticity in the auditory system should lead to harnessing central auditory plasticity for superior clinical technique.

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

Abstract 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.

Plasticity in the developing auditory cortex: evidence from children with sensorineural hearing loss and auditory neuropathy spectrum disorder.

The developing auditory cortex is highly plastic. As such, the cortex is both primed to mature normally and at risk for reorganizing abnormally, depending upon numerous factors that determine central maturation. From a clinical perspective, at least two major components of development can be manipulated: (1) input to the cortex and (2) the timing of cortical input. Children with sensorineural hearing loss (SNHL) and auditory neuropathy spectrum disorder (ANSD) have provided a model of early deprivation of sensory input to the cortex and demonstrated the resulting plasticity and development that can occur upon introduction of stimulation. In this article, we review several fundamental principles of cortical development and plasticity and discuss the clinical applications in children with SNHL and ANSD who receive intervention with hearing aids and/or cochlear implants.

Cortical development and neuroplasticity in Auditory Neuropathy Spectrum Disorder.

Cortical development is dependent to a large extent on stimulus-driven input. Auditory Neuropathy Spectrum Disorder (ANSD) is a recently described form of hearing impairment where neural dys-synchrony is the predominant characteristic. Children with ANSD provide a unique platform to examine the effects of asynchronous and degraded afferent stimulation on cortical auditory neuroplasticity and behavioral processing of sound. In this review, we describe patterns of auditory cortical maturation in children with ANSD. The disruption of cortical maturation that leads to these various patterns includes high levels of intra-individual cortical variability and deficits in cortical phase synchronization of oscillatory neural responses. These neurodevelopmental changes, which are constrained by sensitive periods for central auditory maturation, are correlated with behavioral outcomes for children with ANSD. Overall, we hypothesize that patterns of cortical development in children with ANSD appear to be markers of the severity of the underlying neural dys-synchrony, providing prognostic indicators of success of clinical intervention with amplification and/or electrical stimulation. This article is part of a Special Issue entitled .

The effects of stimulus rate on ABR morphology and its relationship to P1 CAEP responses and auditory speech perception outcomes in children with auditory neuropathy spectrum disorder: evidence from case reports

Abstract Objective: Auditory neuropathy spectrum disorder (ANSD) affects approximately 5–15% of children with sensorineural hearing loss (SNHL). ANSD is characterized by the presence of otoacoustic emissions (OAE) and an absent or abnormal auditory brainstem response (ABR). The purpose of this study was to investigate the prognostic value of slow-rate ABR in predicting the auditory cortical development and auditory speech perception outcomes in case studies of children with ANSD. Design: ABR waveform characteristics were collected at slow stimulation rates (5.1 clicks/second) and a fast stimulation rates (>11–31.1 clicks/second, rates typically used in a clinical setting) in three case reports of children with ANSD. P1 CAEP responses and measures of auditory speech perception using the Infant Toddler Meaningful Auditory Integration Scale (IT-MAIS) were also collected in these children. Retrospective analysis was performed to evaluate the prognostic value of slow- versus fast-rate ABR in predicting P1 CAEP responses and auditory speech perception outcomes in these children. Study sample: Participants included case reports of three paediatric participants with a clinical diagnosis of ANSD. Results: Slow-rate ABR did not elicit significant improvements in waveform morphology compared to fast-rate ABR. P1 CAEP results were present in 2 out of 3 cases and were consistent with auditory speech perception outcomes. Conclusions: Even when ABR stimulation rates were slowed, ABR responses in these children with ANSD did not display any characteristic or replicable pattern, and ABR responses were not predictive of cortical auditory maturation or behavioural performance. In contrast, P1 CAEP responses provided valuable information regarding the maturational status of the auditory cortex and P1 CAEP responses were consistent with behavioural measures of auditory speech perception. Overall, results highlight the high prognostic value of P1 CAEP testing when used in conjunction with behavioural measures of auditory speech perception in children with ANSD.

Developmental Plasticity of the Central Auditory System

Congenital deafness results in a lack of input to the auditory system, hence dramatically altering cortical connectivity and development. Cochlear implants bypass the damaged cochlea by directly stimulating the central nervous system, providing a window into the development of the central auditory system. Converging evidence from studies of deaf animals and children fitted with cochlear implants have allowed us to delineate the characteristics and time course of deprivation-induced and activity-dependent plasticity in the central auditory system. These advances in our understanding of auditory system development can lead to the harnessing of plasticity for improved clinical treatments and outcomes.