Development of Binaural and Spatial Hearing

Processing of Horizontal Sound Localization Cues in Newborn Infants

“…Measured with a visual fixation paradigm, Bundy (1980) demonstrated that 16 week old infants could detect reversals in a 6-dB intensity difference between the two ears, although they were unable to accurately localize the leader sound. He also showed that 8 week old infants could detect the reversals of a 300-µsec time difference between the two ears, but they did not respond to the intensity cue, supporting observations that young infants appear to be more sensitive to interaural time than interaural level difference (Litovsky and Ashmead 1997).…”

“…For instance, regarding the ITD value, a completely lateralized sound source causes a delay of about 411 µsec in neonates, which increases to 660 µsec by adulthood (Clifton et al 1988). Although young infants' localization abilities have been shown to be imprecise (Clifton et al 1988;Litovsky and Ashmead 1997), there exist some findings demonstrating that they are sensitive to the cues required for horizontal sound localization. Measured with a visual fixation paradigm, Bundy (1980) demonstrated that 16 week old infants could detect reversals in a 6-dB intensity difference between the two ears, although they were unable to accurately localize the leader sound.…”

“…However it is estimated that they can only detect an azimuth change of the sound source position exceeding 30° (Morrongiello et al 1994). The minimum detectable angle (Mills, 1958) decreases to about 14° by 7 months (Litovsky and Ashmead 1997), reaching the adult level of 1° by 5 years of age (Litovsky 1997), showing a prolonged developmental trajectory for sound localization acuity during childhood.…”

“…One caveat of the behavioral measures is that it is difficult to study young infants' sound localization abilities before ~ 4 months of age, because, due to the maturation of higher cortical mechanisms that take place during the first three months, the head-orienting response cannot be reliably elicited before that age (Muir and Clifton 1985;Litovsky and Ashmead 1997). By measuring short-latency electrophysiological responses, such as ABR and MLR, previous results have indicated that the auditory pathways responsible for sound localization are functional at 5 birth (Jiang and Tierney, 1996;Cone-Wesson, Ma and Fowler, 1997;Furst et al, 2004).…”

El desarrollo auditivo en la primera infancia: Compendio de evidencias científicas relevantes para el profesorado

“…En cuanto a la localización de sonidos en el espacio, Munar et al (2002) señalan que los neonatos presentan una audición bastante refleja del espacio, sin embargo, desde los cuatro o cinco meses comienzan a desarrollar una localización espacial, la cual madura progresivamente durante el crecimiento fisiológico, logrando alcanzar el nivel de rendimiento de una persona adulta recién en la adolescencia (Litovsky y Ashmead, 1997). Según Hüg y Arias (2009), la evidencia experimental obtenida permite establecer que los neonatos son capaces de orientar su cabeza hacia los sonidos de manera lenta y poco precisa, no obstante, a los cuatro o cinco meses de edad muestran una respuesta más rápida y precisa, acompañada de la búsqueda visual y logran, a los seis meses, percibir ciertos cambios angulares en la ubicación de las fuentes sonoras tanto en plano vertical como horizontal, sobretodo, cuando consiguen adoptar la postura de sentado.…”