Abstract
Language development relies on early auditory exposure, both in utero and the first year of life. During this time, infants undergo vast structural and sensory development, while experiencing sensory inputs that impact the auditory system. This presentation will outline the progression of auditory development and impact of early exposures. Findings from a recent study that quantified types of auditory exposures across infant environments and potential clinical implications will be discussed.
Primary Author and Speaker: Lara Liszka
Additional Authors and Speakers: Maggie Crabtree
Contributing Authors: Roberta Pineda
The transition to the external world after full gestation results in the infant being exposed to unbuffered high frequency sounds, which are timed after the auditory system is developed. When infants are born preterm, the sequence of timed auditory exposure is interrupted. Although research has been conducted on infant auditory development and positive auditory exposures in the neonatal intensive care unit (NICU), no research has reported the similarities and differences between auditory exposures in various infant environments.
This is a prospective, longitudinal, descriptive study of quantitative data. Three groups of infants (n=128) were included in this study and were enrolled between August 2012- March 2018. The preterm group (n=48) consisted of infants born at < 28 weeks gestation. All infants were hospitalized in a level IV NICU at St. Louis Children’s Hospital, St. Louis, Missouri. Exclusion criteria included congenital anomalies, failed hearing screening, and multiple birth. The labor and delivery floor group (n=50) consisted of infants born ≥38 weeks gestation. All infants were hospitalized on the labor and delivery floor of Barnes-Jewish Hospital, St. Louis, Missouri. The home environment group (n=25) consisted of infants born < 28 weeks gestation who had been discharged from the level IV NICU at St. Louis Children’s Hospital, St. Louis, Missouri.
The Language Environmental Acquisition (LENA Research Foundation, Boulder, Colorado) device was used to collect the types and quantity of auditory exposures across a 16-hour period. LENA Pro Software was used to calculate estimated amounts of time in which the primary auditory stimulus was meaningful words, distant words, electronic sounds, noise, and silence. In addition, LENA ADEX software was used to calculate the peak and average decibel levels of auditory stimuli in the infant’s auditory environment as well as the number of adult words spoken in the infant’s environment across the 16-hour period. One-way ANOVA (p<0.05) was used to determine differences in different auditory exposures between groups.
There was significantly more meaningful and distant language on the labor and delivery floor than in the NICU and home environment (p<0.001). There were more adult words on the labor and delivery floor than in the NICU and home environment (p<0.001), with an average of 14,119.8 more words than the NICU and 13,844.0 more words than the home environment in the 16-hour period. There was significantly less silence on the labor and delivery floor than in the NICU and home environment (p<0.05), with an average of 1 hour, 2 minutes less than the NICU and an average 3 hours, 1 minute less than the home environment within the 16-hour period. The NICU had significantly more noise than the home environment of preterm infants, with an average of 1 hour, 18 minutes more within the 16-hour period. Average sound levels in the NICU were 57.2 + 2.3 dB with an average peak level of 87.2 + 1.2 dB; average sound levels for full-term infants on the labor and delivery floor were 63.3 + 2.2 dB, with an average peak level of 87.0 + 1.3 dB. Average sound levels in the home environment of preterm infants were 56.4 + 4.6 decibels, with an average peak level of 86.4 + 1.5 dB.
The NICU and home environment of preterm infants offered less language exposure than the labor and delivery floor where full-term infants were hospitalized. Understanding how full-term infants experience differing auditory exposures than preterm infants in the NICU and the home paves the way for interventions that enhance positive forms of auditory exposures for preterm infants. Clinicians working with these infants can educate families and clinicians on the importance of positive auditory exposures.
Aslin, R.N., et al., Discrimination of voice onset time by human infants: new findings and implications for the effects of early experience. Child development, 1981. 52(4): p. 1135-45. https://doi.org/10.2307/1129499
Eilers, R.E., et al., Discrimination of voice onset time in infancy. The Journal of the Acoustical Society of America, 1981. 70(4): p. 955-65. https://doi.org/10.1121/1.387024
Landolfi, E., et al., The development of language in babies and the role of the family. The Journal of Maternal-Fetal & Neonatal Medicine, 2011. 24 Suppl 1: p. 120-1.https://doi.org/10.3109/14767058.2011.607611
Werker, J.F. and R.C. Tees, Speech perception as a window for understanding plasticity and commitment in language systems of the brain. Developmental psychobiology, 2005. 46(3): p. 233-51. https://doi.org/10.1002/dev.20060