Development of human peripheral hearing revealed by brainstem auditory evoked potentials

Abstract

Development of human peripheral hearing from birth to 6 years was investigated by recording brainstem auditory evoked potentials (BAEPs). The threshold of BAEPs decreased rapidly during the first 3 months after birth (2.7 dB/week during the neonatal period, 2.6 dB/month at 1-3 months), after which further decrease occurred more slowly but continued through 1 year of age (0.26 dB/month at 3-12 months). A few days after birth, the threshold was 18 dB higher compared to the adults, and progressively decreased to 10, 5 and 2 dB at 1, 3 and 12 months, respectively. The latencies of waves I and V decreased as a function of age at a rate of 0.01 and 0.05 ms/week during the neonatal period, 0.02 and 0.10 ms/month at 1-3 months and 0.014 and 0.076 ms/month at 3-12 months, respectively. Adult latency value was attained by 2 and 4 years for waves I and V, respectively. These findings suggest that although the ear is reported to be almost adult-like at birth, the immaturity in neural functional properties limits auditory sensitivity during early childhood. It appears that human peripheral hearing threshold decreases rapidly through the third postnatal month and thereafter continues to improve slowly through early childhood. It is postulated that the first 3 months after birth are likely to be a critical period in postnatal development of human peripheral hearing.