Audition: Hearing and deafness

Abstract

Among the senses, the mechanical ones, hearing, balance, touch, and proprioception, are most numerous but least understood. The status of hearing is very specific. This sense is deeply rooted in social living that requires effective means of communication. In many species, communication is ensured by sounds. Animals produce a large variety of sounds; some are nonvocal, while others are vocal. Some species only produce innate vocalizations, whereas others, such as singing birds and some mammals, like bats, dolphins, elephants, are vocal learners. Audition is a prerequisite for vocal learning. Without auditory experience, juveniles will not be able to produce an adult form of sound. Human evolution is characterized by the development of acoustic communication with speech and language, that is, by the development of an unparalleled ability of making sense out of sounds, which involves the rapid decoding of the spectrotemporal properties of the acoustic signals to extract both phonetic and linguistic information. Hearing-impaired babies could never reach normal proficiency in their mother language if they were not screened and diagnosed early enough, specifically, within months at most, and hard-of-hearing aging people become dangerously isolated. Both populations require appropriate and fast intervention, which concerns not less than several hundred million people worldwide. Therefore, better understanding how hearing works, from peripheral sensory organs to the brain, is a long-lasting challenge of prominent importance.