The Auditory Sensitivity is Increased in Tinnitus Ears

Increased auditory sensitivity, also called hyperacusis, is a pervasive complaint of people with tinnitus. The high prevalence of hyperacusis in tinnitus subjects suggests that both symptoms have a common origin. It has been suggested that they may result from a maladjusted increase of central gain attributable to sensory deafferentation. More specifically, tinnitus and hyperacusis could result from an increase of spontaneous and stimulus-induced activity, respectively. One prediction of this hypothesis is that auditory sensitivity should be increased in tinnitus compared with non-tinnitus subjects. The purpose of this study was to test this prediction by examining the loudness functions in tinnitus ears (n = 124) compared with non-tinnitus human ears (n = 106). Because tinnitus is often accompanied by hearing loss and that hearing loss makes it difficult to disentangle hypersensitivity (hyperacusis) to loudness recruitment, tinnitus and non-tinnitus ears were carefully matched for hearing loss. Our results show that auditory sensitivity is enhanced in tinnitus subjects compared with non-tinnitus subjects, including subjects with normal audiograms. We interpreted these findings as compatible with a maladaptive central gain in tinnitus.