Monaural occlusion alters sound localization during a sensitive period in the barn owl

Abstract

Sound localization was disrupted in young barn owls by chronically plugging one ear. Owls that were younger than 8 weeks of age at the time of ear plugging recovered normal localization accuracy while plugged, whereas those that were older than 8 weeks at the time of ear plugging did not. The end of the sensitive period for the adjustment of sound localization accuracy coincides with the maturation of the head and ears, suggesting that the exposure of the auditory system to stable, adult-like acoustic cues could play a role in bringing the sensitive period to a close. The results demonstrate that, early in development, associations between auditory cues and locations in space can be altered by experience.Animals localize sounds by associating sets of monaural and binaural cues with locations in space. The most reliable cues are binaural, i.e., differences in the timing and intensity of sounds at the two ears. The reliability of these cues results from the fact that they depend only upon the size and shape of the head and ears and do not require assumptions about the properties of the original sound stimulus or the acoustic environment (Searle et al., 1976). Therefore, once the auditory system is calibrated to the passive acoustic properties of the head and ears and correlates frequency-specific binaural differences with locations in space, these binaural cues become unconditional indicators of the location of a sound source.In the course of normal development, growth of the head and ears increases the range of binaural disparities experienced by the auditory system and alters the correlations of binaural cues with locations in space. Among adults, the size of the head and ears varies; therefore the associations between binaural cues and locations in space differ slightly for each individual. In light of this variability, how does the auditory system establish correct associations between binaural cues and locations in space? One solution might be that calibration of the sound localization circuitry is based upon sensory experience. To explore this possibility we have investigated

Conductive Hearing Loss Induced by Experimental Middle-Ear Effusion in a Chinchilla Model Reveals Impaired Tympanic Membrane-Coupled Ossicular Chain Movement

“…CM recordings have been used previously to gather information about how CHL (including MEE-induced CHL) alters the acoustic cues to sound location (Knudsen et al 1984;Hartley and Moore 2003;Lupo et al 2011;Thornton et al 2012). Additionally, CM measurements provide information about the efficiency of the middle ear in transferring sound energy from the external ear canal, through the middle ear, and ultimately to the inner ear.…”

Impaired Binaural Hearing in Children Produced by a Threshold Level of Middle Ear Disease

“…More recent research provides further support for changes in auditory brain function (Moore et al 1999;King et al 2000;Tucci et al 2001). However, while the effects of visual form deprivation and interocular misalignment in infancy are profound and relatively well understood, the early, mild, asymmetric conductive hearing loss produced by OME (Kokko 1974;Gravel and Wallace 2000; or, experimentally, by occlusion of the ear canal (Knudsen et al 1984;Moore et al 1989Moore et al , 1999King et al 2000) or malleus removal (Cook et al 2002) seems to exert a more subtle influence on central auditory processing.…”

“…1A) and incidence (Hogan et al 1997(Hogan et al , 1998Paradise et al l997;Hogan 1999) of otitis media with effusion (OME, also known as ''glue ear'') in early childhood has generated much speculation concerning its effect on the development of the human auditory system and on language acquisition and perception. Concern about the effects of OME as a form of auditory deprivation was further heightened by research from animal studies, first in the visual system (Wiesel and Hubel 1965;Sherman and Spear 1982) and later in the auditory system (Knudsen et al 1984;Moore et al 1989), showing that abnormal sensory experience could produce long-term changes in the structure and function of the primary brain circuits responsible for vision and hearing. More recent research provides further support for changes in auditory brain function (Moore et al 1999;King et al 2000;Tucci et al 2001).…”

Sustained Perceptual Deficits from Transient Sensory Deprivation

“…For example, temporary unilateral deprivation causes binaural encoding deficits that can account for behavioral impairments in sound localization and other binaural tasks (Clements and Kelly, 1978;Moore and Irvine, 1981;Knudsen et al, 1984b;Knudsen, 1985;Mogdans and Knudsen, 1992Moore et al, 1999;Popescu and Polley, 2010;Keating et al, 2013Keating et al, , 2015Polley et al, 2013). In addition, the clinical literature suggests that hearing loss can disrupt mechanisms associated with cognitive processing (Uhlmann et al, 1989;Arlinger, 2003;Lin et al, 2013).…”