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.

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. 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.

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.

Under conditions of profound sensory deprivation, the brain has the propensity to reorganize. For example, intact sensory modalities often recruit deficient modalities’ cortices for neural processing. This process is known as cross-modal reorganization and has been shown in congenitally and profoundly deaf patients. However, much less is known about cross-modal cortical reorganization in persons with less severe cases of age-related hearing loss (ARHL), even though such cases are far more common. Thus, we investigated cross-modal reorganization between the auditory and somatosensory modalities in older adults with normal hearing (NH) and mild-moderate ARHL in response to vibrotactile stimulation using high density electroencephalography (EEG). Results showed activation of the somatosensory cortices in adults with NH as well as those with hearing loss (HL). However, adults with mild-moderate ARHL also showed robust activation of auditory cortical regions in response to somatosensory stimulation. Neurophysiologic data exhibited significant correlations with speech perception in noise outcomes suggesting that the degree of cross-modal reorganization may be associated with functional performance. Our study presents the first evidence of somatosensory cross-modal reorganization of the auditory cortex in adults with early-stage, mild-moderate ARHL. Our findings suggest that even mild levels of ARHL associated with communication difficulty result in fundamental cortical changes.

Sensory dysfunction is a core symptom of autism spectrum disorder (ASD), and abnormalities with sensory responsivity and processing can be extremely debilitating to ASD patients and their families. However, relatively little is known about the underlying neuroanatomical and neurophysiological factors that lead to sensory abnormalities in ASD. Investigation into these aspects of ASD could lead to significant advancements in our general knowledge about ASD, as well as provide targets for treatment and inform diagnostic procedures. Thus, the current study aimed to measure the covariation of volumes of brain structures (i.e., structural magnetic resonance imaging) that may be involved in abnormal sensory processing, in order to infer connectivity of these brain regions. Specifically, we quantified the structural covariation of sensory-related cerebral cortical structures, in addition to the cerebellum and amygdala by computing partial correlations between the structural volumes of these structures. These analyses were performed in participants with ASD (n = 36), as well as typically developing peers (n = 32). Results showed decreased structural covariation between sensory-related cortical structures, especially between the left and right cerebral hemispheres, in participants with ASD. In contrast, these same participants presented with increased structural covariation of structures in the right cerebral hemisphere. Additionally, sensory-related cerebral structures exhibited decreased structural covariation with functionally identified cerebellar networks. Also, the left amygdala showed significantly increased structural covariation with cerebral structures related to visual processing. Taken together, these results may suggest several patterns of altered connectivity both within and between cerebral cortices and other brain structures that may be related to sensory processing.