Morphological and Functional Development of the Auditory Nervous System

Three-month-olds discriminate resolved harmonic complexes on the basis of missing fundamental (MF) pitch. In view of reported difficulty in discriminating unresolved complexes at 7 months and striking changes in the organization of the auditory system during early infancy, infants' ability to discriminate unresolved complexes is of some interest. This study investigated the ability of 3-month-olds, 7-month-olds, and adults to discriminate the pitch of unresolved harmonic complexes using an observer-based method. Stimuli were MF complexes bandpass filtered with a À12 dB/octave slope, combined in random phase, presented at 70 dB sound pressure level (SPL) for 650 ms with a 50 ms rise/fall with a pink noise at 65 dB SPL. The conditions were (1) "LOW" unresolved harmonics (2500-4500 Hz) based on MFs of 160 and 200 Hz and (2) "HIGH" unresolved harmonics (4000-6000 Hz) based on MFs of 190 and 200 Hz. To demonstrate MF discrimination, participants had to ignore spectral changes in complexes with the same fundamental and respond only when the fundamental changed. Nearly all infants tested categorized complexes by MF pitch suggesting discrimination of pitch extracted from unresolved harmonics by 3 months. Adults also categorized the complexes by MF pitch, although musically trained adults were more successful than musically untrained adults.

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Perception of the pitch of unresolved harmonics by 3- and 7-month-old human infants

Lau

Werner

2014

“…Auditory cortex is markedly immature in the early months of infancy (Moore and Linthicum, 2007). In fact, Eggermont and Moore (2012) have suggested that the thalamocortical pathway is not functional at this early age and that cortical responses recorded in young infants are generated through a reticular activating system projection to neurons in cortical layer I. This reticular-cortical pathway is held to act as a change detection system, leading infants to respond to changes in speech or other sounds, based on the representation of those sounds provided by the auditory brainstem.…”

Section: Discussionmentioning

confidence: 99%

Perception of missing fundamental pitch by 3- and 4-month-old human infants

Lau

Werner

2012

A hallmark of complex pitch perception is that the pitch of a harmonic complex is the same whether or not the fundamental frequency is present. By 7 months, infants appear to discriminate on the basis of the pitch of the missing fundamental (MF). Although electrophysiological cortical responses to MF pitch changes have been recorded in infants younger than 7 months, no psychophysical studies have been published. This study investigated the ability of 3-and 4-month-olds to perceive the pitch of MF harmonic complexes based on fundamentals of 160 Hz and 200 Hz using an observer-based method. In experiment I, to demonstrate MF pitch discrimination, 3-and 4-month-olds were required to ignore spectral changes in complexes with the same fundamental and to respond only when the fundamental changed. In experiment II, a 60-260 Hz noise was presented with complexes to mask combination tones at the fundamental frequency. In experiment III, complexes were bandpass filtered with a À12 dB/octave slope to limit use of spectral edge cues and presented with a pink noise to mask all distortion products. Nearly all infants tested categorized complexes by MF pitch in these experiments, suggesting perception of the missing fundamental at 3 months.

“…Growth of the external and middle ear from a young child to adult increases the volumes of the ear canal and middle-ear cavity, and changes the orientations between ossicles (particularly in newborn infants) (Abdala and Keefe, 2012;Qi et al, 2008). The developmental alterations of the human ear affect the dynamic characteristics of the peripheral auditory system and sound energy transmission into the cochlea (Eggermont and Moore, 2012). Understanding the acoustic response properties of the pediatric ear has important implications for interpretation of middle-ear assessment measures of pediatric hearing.…”

Section: Introductionmentioning

confidence: 99%

Predictions of middle-ear and passive cochlear mechanics using a finite element model of the pediatric ear

Wang

Keefe

Gan

2016

A finite element (FE) model was developed based on histological sections of a temporal bone of a 4-year-old child to simulate middle-ear and cochlear function in ears with normal hearing and otitis media. This pediatric model of the normal ear, consisting of an ear canal, middle ear, and spiral cochlea, was first validated with published energy absorbance (EA) measurements in young children with normal ears. The model was used to simulate EA in an ear with middle-ear effusion, whose results were compared to clinical EA measurements. The spiral cochlea component of the model was constructed under the assumption that the mechanics were passive. The FE model predicted middle-ear transfer functions between the ear canal and cochlea. Effects of ear structure and mechanical properties of soft tissues were compared in model predictions for the pediatric and adult ears. EA responses are predicted to differ between adult and pediatric ears due to differences in the stiffness and damping of soft tissues within the ear, and any residual geometrical differences between the adult ear and pediatric ear at age 4 years. The results have significance for predicting effects of otitis media in children.