Auditory temporal processing ability and the development of speech, language and reading: implications for children with auditory neuropathy spectrum disorder

Auditory Neuropathy Spectrum Disorder (ANSD) is classified by normal cochlear mechanical function but severely degraded neural synchrony. The auditory system relies on high levels of neural synchrony for processing timing (temporal) cues which are critical for speech perception (particularly in degraded conditions) and normal speech, language and reading development. Unlike most sensorineural hearing losses, speech perception ability in ANSD appears to be correlated with the magnitude of temporal disruption rather than spectral disruption (measured either through the pure tone audiogram or estimated by frequency-specific auditory brainstem responses; ABR). Because ANSD is mostly diagnosed in infants through newborn hearing screening programs, objective tests of temporal processing are needed. The current study focused on the development and evaluation of objective tests of temporal processing for children. Specifically, the aims of the present study were to: identify the likely types of disruptions that occur to speech perception, language and reading abilities in young children with abnormal temporal processing, and the magnitude of disruption that can affect these skills; develop and evaluate objective measures of temporal processing in normally hearing adults to provide sensitive measures of assessing different auditory temporal processing abilities; and evaluate the applicability of these objective measures to normally hearing children (aged 5-12) with normal speech, language and reading abilities and to normally hearing older adults with poor temporal processing abilities (aged 64-80 years). This study provides normative data for objective temporal processing measures, which ultimately can be used to evaluate temporal processing abilities in children with ANSD unable to provide behavioural responses. Because of the heterogeneous nature of the disorder and co-morbidity of other medical problems in this population, research in this area is limited. Nonetheless, developing a greater understanding of this problem is critical to improved management of children diagnosed with ANSD and other temporal deficits.