Development of the auditory system

Abstract

Auditory development involves changes in the peripheral and central nervous system along the auditory pathways, and these occur naturally, and in response to stimulation. Human development occurs along a trajectory that can last decades, and is studied using behavioral psychophysics, as well as physiologic measurements with neural imaging. The auditory system constructs a perceptual space that takes information from objects and groups, segregates sounds, and provides meaning and access to communication tools such as language. Auditory signals are processed in a series of analysis stages, from peripheral to central. Coding of information has been studied for features of sound, including frequency, intensity, loudness, and location, in quiet and in the presence of maskers. In the latter case, the ability of the auditory system to perform an analysis of the scene becomes highly relevant. While some basic abilities are well developed at birth, there is a clear prolonged maturation of auditory development well into the teenage years. Maturation involves auditory pathways. However, non-auditory changes (attention, memory, cognition) play an important role in auditory development. The ability of the auditory system to adapt in response to novel stimuli is a key feature of development throughout the nervous system, known as neural plasticity.

Bilateral cochlear implants in children: Effects of auditory experience and deprivation on auditory perception

“…A common metric is the minimum audible angle (MAA) [9, 10]. For recent reviews on this topic see also [5, 6]. A second measure is localization accuracy, which is informative regarding the ability of a listener to identify the location of a sound source from amongst an array of sources; accuracy can be measured for sound sources along the vertical or horizontal dimension but in bilateral CI users the focus has been on the horizontal plane, where binaural cues would be most effectively utilized [11].…”

“…In children with normal hearing (NH), spatial hearing abilities are fairly well developed by age 4–5 years [5] [6]. However, it is likely that the ability to achieve good level of functioning regarding spatial hearing depends on the child’s access to normal acoustic cues.…”

Does Bilateral Experience Lead to Improved Spatial Unmasking of Speech in Children Who Use Bilateral Cochlear Implants?

“…That is, having access to sound in two ears is useful from the perspective of being able to listen to whichever ear has a better signal-to-noise ratio (SNR). For reviews on this topic see ([22] [4] [2]). Today’s clinical treatments for providing input to both ears consist primarily of a cochlear implant in each ear, or for children with residual hearing in one or both ears, combining implantation with acoustic hearing could have benefits as well [23, 24].…”

“…This integration, in normal hearing systems, is mediated by an intricate neuronal circuitry in the brainstem, with auditory mechanisms that are tuned to spatial information. In children with normal hearing (NH), the spatial system utilizes binaural cues with great precision, and the development of the neural circuitry is fairly refined by 4–5 years of age [1] [2]. This early development of spatial hearing likely depends on experience with normal acoustic cues.…”

Electrophysiological Threshold Evaluation in Infants with and Without Risk Indicators for Hearing Loss

“…Another interesting aspect to be explained is that the peripheral portion of the auditory system is developed between the fifth and sixth month of gestation and the structures of the central portion continue to form synaptic connections and improve their efficiency during the first two years of life, so the electrophysiological threshold and wave latency may change during this period [8,9]. In addition, variables such as: age, body temperature, middle ear effusion and hypoxic-ischemic lesions may cause transient changes in the test result [10][11][12]. Consequently, the preliminary findings of BAEP may not correspond to the final hearing status [1,6,7,13].…”