Chapter 7 - Effects of “Nondamaging Sound” on the Adult Auditory Brain

Abstract

Adult auditory plasticity is represented in learning and training effects on the brain. Adult auditory plasticity is also reflected in the acclimatization time course to full usefulness of new hearing aids and cochlear implants. Even simple manipulations, such as long-term plugging the ears or exposing them to relatively soft sound, profoundly affect the loudness perception measured afterwards and also produces changing neural activity in auditory cortex, thalamus and midbrain. Most of these changes have been demonstrated in animals following long-term exposure to behaviorally irrelevant sound and appear to be very long lasting. The induced changes, in tonotopic maps, in spontaneous and stimulus-driven firing rates and in neural synchrony, take several weeks of exposure to fully develop and then recover in quiet over a period that extends over at least three months. The findings illustrate potentially destructive effects of moderate long-term sound exposure on speech understanding in children and adults in the absence of audiometric hearing loss.