In addition to presenting complex stimuli such as music or syllables, a person’s capability to discriminate rapidly presented auditory information can be evaluated by varying click-stimulus presentation rates and through forward- or backward-masking paradigms. In addition to simple auditory thresholds and the time it takes to perceive stimuli, the ability to process more complex auditory stimuli and to engage in rapid auditory processing, has been found to relate to the development of language and reading skills, as well as being a potential marker for dyslexia, autism and early hearing loss 7, 8. Researchers and clinicians in a variety of fields have become increasingly interested in the function of auditory processing in subcortical pathways. In particular, Wave V, which occurs roughly 6 ms after stimulus onset, is frequently used as an indicator not only of auditory processing but also the neurological integrity of the auditory system 6. Thus, ABRs in young children can give information about central nervous system maturation. Although these ABR components are similar in adults, their timing and amplitude in infants show longer latencies and less consistent amplitudes due in part to incomplete myelination of the auditory system. ![]() The ABR components in newborns and young infants typically consist of three well-defined wave forms, Wave I (representing activity at the cochlear nerve), Wave III (activation at the cochlear nucleus) and Wave V (reflecting activity at the lateral lemniscus) 5. It has been used in hearing screening and clinical diagnosis for both audiological and neurological impairments, such as conductive and sensorineural hearing loss, cochlear lesions, tumors of the auditory nerve and brainstem lesions 1, 2, 3, 4. The auditory brainstem response (ABR) to click stimuli can provide precise information about the functional integrity of the brainstem and other auditory structures. The greatest improvements in Wave V latencies from 6 weeks to 9 months of age were observed in the 64-ms masker-probe interval, suggesting that central auditory nervous system related to the temporal processing at this interval might undergo rapid development during the first year of life. Results showed that as masker-probe intervals became longer and as infants got older, Wave V latency to the probe shortened. ![]() Infants were presented with pairs of stimuli (an initial “masker” followed by a “probe”) separated by different time intervals (8, 16 and 64 ms). Our purpose was to establish normative values of forward-masking ABRs and investigate the development of auditory temporal processing in infants at these ages. In the present study, auditory brainstem responses (ABRs) were recorded in a forward-masking paradigm in healthy, full-term infants aged 6 weeks (n = 111) and 9 months (n = 62). Early auditory temporal processing abilities are important for language acquisition and for later reading abilities.
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