As the intensity of a sound increases, typical-hearing listeners experience an increase in loudness, but for levels above 120 decibels (dB), listeners not only perceive the sound as extremely loud, but also painful—the aural threshold of pain. Some individuals with hearing loss and other neurological disorders perceive even moderate-intensity sounds as both painful and loud, a condition known as pain hyperacusis.
Validating an Animal Model of Hyperacusis
To learn what is happening in the brain and nervous system when hyperacusis is present, we used sound-evoked, functional magnetic resonance imaging (fMRI) to locate regions of abnormal activity in the central nervous system of rats with behavioral evidence of hyperacusis induced with an ototoxic drug (sodium salicylate). We observed enhanced central auditory gain and were able to confirm this electrophysiologically.