Auditory Development

Auditory development is the study of the sequence of events that lead to mature audition, or hearing, which plays an important role in the acquisition of spoken language, comprehension of speech, and the ability to localize sounds and navigate [Page 212]around acoustically complex real-world environments. The goal of auditory processing is to reconstruct a scene of auditory objects that can be identified by the listener (e.g., I hear four people talking at a table in a noisy restaurant). Importantly, a listener must also be able to extract meaning from this auditory scene. The endpoint of development is a mature auditory system that can accomplish this task with accuracy and efficiency. This entry discusses the structural, functional, and perceptual development of the auditory system.

The study of auditory development considers the maturation of each stage involved in the processing of sound. Sound is first conducted by the outer and middle ear into the inner ear where it is encoded as a sequence of auditory nerve fiber action potentials. The waveform of each sound is represented by the aggregate of all auditory nerve fiber responses. The central auditory system then extracts the features of sound that are important for the separation of simultaneous sounds, the formation of auditory objects, and ultimately, the determination of meaning. Specific neural structures in the auditory pathway are associated with each stage of processing.

To add further complexity, both cortical and subcortical structures exert top-down influence on how sound is encoded and extracted in the ear and the auditory nerve. Consequently, auditory processing involves all the structures along the auditory pathway, beginning with the encoding of sound at the ear and ending with the understanding of sound by the brain. Immaturity at any stage of processing can lead to differences in the coding, transmission, or perception of sound. Moreover, immaturity anywhere in the ear, brainstem, or cortex can result in similar patterns of immature hearing.

The human auditory system undergoes an extended period of development from conception to adolescence. Although some aspects of the primary auditory processes—which refers to the representation of frequency, intensity, and temporal fluctuations in a sound—may mature early, prolonged development of more complex abilities such as speech perception, music perception, and listening in noise is observed well into the adolescent years. In addition to maturation of the auditory pathway, changes in attention, memory, and cognition also influence the development of auditory perception.

A central question addressed in the study of auditory development is how the physical growth (structural development) and the onset of activity (functional development) in the ear and the brain relate to the emergence of auditory abilities (perceptual development). Thus, the study of auditory development can be divided into these three main areas of focus: structural, functional, and perceptual development.