Pure-Tone Frequency Discrimination in Preschoolers, Young School-Age Children, and Adults

Unveiling the development of human voice perception: Neurobiological mechanisms and pathophysiology

The human voice is a critical stimulus for the auditory system that promotes social connection, informs the listener about identity and emotion, and acts as the carrier for spoken language. Research on voice processing in adults has informed our understanding of the unique status of the human voice in the mature auditory cortex and provided potential explanations for mechanisms that underly voice selectivity and identity processing. There is evidence that voice perception undergoes developmental change starting in infancy and extending through early adolescence. While even young infants recognize the voice of their mother, there is an apparent protracted course of development to reach adult-like selectivity for human voice over other sound categories and recognition of other talkers by voice. Gaps in the literature do not allow for an exact mapping of this trajectory or an adequate description of how voice processing and its neural underpinnings abilities evolve. This review provides a comprehensive account of developmental voice processing research published to date and discusses how this evidence fits with and contributes to current theoretical models proposed in the adult literature. We discuss how factors such as cognitive development, neural plasticity, perceptual narrowing, and language acquisition may contribute to the development of voice processing and its investigation in children. We also review evidence of voice processing abilities in premature birth, autism spectrum disorder, and phonagnosia to examine where and how deviations from the typical trajectory of development may manifest.

Cortical auditory-evoked potential as a biomarker of central auditory maturation in term and preterm infants during the first 3 months

OBJECTIVES

To analyze central auditory maturation in term and preterm infants during the first 3 months of life by comparing the latency and amplitude of cortical auditory-evoked potential at different frequencies.

METHODS

In this study, 17 term and 18 preterm infants were examined; all had tested positive on the neonatal hearing screening test. Cortical auditory potential was investigated during the first and third months of life. The response of the cortical auditory-evoked potential was investigated at frequencies of 500, 1000, 2000, and 4000 Hz. The latency and amplitude of the cortical response were automatically detected and manually analyzed by three researchers with experience in electrophysiology. The results were compared using analysis of variance and the Bonferroni test. A significance level of 5% was used for all analyses.

RESULTS

Latency values of cortical auditory-evoked potential in the first month of birth were significantly higher than those in the third month, and latency values of the preterm group were higher than those of the term group, regardless of the frequency and time of evaluation. In general, the latency of the cortical auditory-evoked potential was higher at high frequencies. Amplitude values in the third month of life were significantly higher than those in the first month for term and preterm infants.

CONCLUSION

Central auditory maturation was observed in both groups but with different results between those born at term and preterm, with latencies of cortical auditory-evoked potential higher for the preterm group and at high frequencies.

Auditory Development of Frequency Discrimination at Extended High Frequencies

OBJECTIVES

Hearing in the extended high frequencies (EHFs; >8 kHz) is perceptually and clinically relevant. Recent work suggests the possible role of EHF audibility in natural listening environments (e.g., spatial hearing) and hidden hearing loss. In this article, we examine the development of frequency discrimination (FD) in the EHFs. Specifically, the objectives of the present study were to answer if the developmental timeline for FD is different for EHFs; and whether the discontinuity of FD thresholds across frequency-representing the hypothetical shift from a temporal to place code-for children occurs at about the same frequency as adults.

DESIGN

Thirty-one normal-hearing children (5 to 12 years) and 15 young adults participated in this study. FD thresholds were measured for standard frequencies (1, 2, 4, 6, and 8 kHz) and EHFs (10 and 12.5 kHz) using a three-alternative (odd-ball) forced-choice paradigm. Statistical analysis focused on examining the change of FD thresholds as a function of age and estimating the breakpoints in the discrimination threshold-frequency functions.

RESULTS

FD performance in younger children for EHFs was nearly six times poorer relative to older children and adults; however, there was no effect of test frequency on the child-adult difference. Change-point detection on group data revealed a higher knot frequency-representing the putative transition from temporal to place mechanisms-for adults (9.8 kHz) than children (~6 kHz). Individual spline functions suggest that the knot frequency varied from 2 to 10 kHz across participants.

CONCLUSIONS

The present study provides evidence for a similar rate of maturation of FD for EHFs and standard frequencies. FD at EHFs matures by 10 to 12 years of age. Adult listeners may not all use temporal cues up to 10 kHz. Young children are relatively inefficient in using temporal fine-structure cues for FD at frequencies above 6 kHz.

The development of auditory functions

Typical development and maturation of the auditory system, at both the peripheral and central levels, is essential for the acquisition of speech, language, and auditory skills. The peripheral system generally encodes three basic parameters associated with auditory stimuli-time, frequency, and intensity. These acoustic cues are subsequently processed by the central auditory structures to reach and be perceived by the cerebral cortex. Observations of the human fetal and neonatal ear indicate that the peripheral auditory system is structurally and functionally adult-like at birth. In contrast, the central auditory system exhibits progressive anatomical and physiologic changes until early adulthood. Enriched experience with sound is fundamental and critical to auditory development. The absence of early and prolonged acoustic stimulation delays neuronal maturation, affecting the central auditory nervous system, in particular, and leading to atypical development. The present chapter reviews the various stages of development of the auditory system structures, especially the embryology of the human ear, before briefly presenting the trajectories of typical development of auditory abilities from infants to school-aged children.