Rapid increases of gamma power in the auditory cortex following noise trauma in humans

Tinnitus is an auditory perception in the absence of any external sound source. It has been suggested that tinnitus is related to enhanced synchronization of neuronal activity in the auditory cortex. Usually a hearing damage can be identified suggesting auditory deprivation to central auditory regions to be fundamental for neurophysiological processes related to tinnitus. Until now, human research has been conducted on patients with chronic tinnitus (>6 months). However, neuronal activity accompanying auditory deprivation and putatively tinnitus may not remain constant over time, making it difficult to directly relate outcomes of current animal studies (acute tinnitus) to chronic tinnitus in humans, and vice versa. We investigated 14 amateur rock musicians who frequently reported a short-term tinnitus immediately after band practice. Magnetoencephalographic resting-state recordings, audiometry and tinnitus testing were performed at two separate occasions: with and without previous exposure to loud music. Analyses revealed that transient tinnitus was accompanied by temporary hearing loss in both ears and increased gamma activity in the right auditory cortex in 13 out of 14 cases. Additionally, tinnitus frequency was strongly correlated to hearing loss. Analogous to animal studies, our results show for the first time in humans that noise trauma leads rapidly to increased neuronal synchrony in the auditory cortex. Importantly, the strongly right-lateralized effect implies that it does not reflect tinnitus percept per se. This could rather have been triggered by greater discontinuities of hearing loss at high frequencies that were particularly pronounced in the left ear.