Effects of Acoustic Environment on Tinnitus Behavior in Sound-Exposed Rats
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Laboratory studies often rely on a damaging sound exposure to induce tinnitus in animal models. Because the time course and ultimate success of the induction process is not known in advance, it is not unusual to maintain sound-exposed animals for months while they are periodically assessed for behavioral indications of the disorder. To demonstrate the importance of acoustic environment during this period of behavioral screening, sound-exposed rats were tested for tinnitus while housed under quiet or constant noise conditions. More than half of the quiet-housed rats developed behavioral indications of the disorder. None of the noise-housed rats exhibited tinnitus behavior during 2 months of behavioral screening. It is widely assumed that the “phantom sound” of tinnitus reflects abnormal levels of spontaneous activity in the central auditory pathways that are triggered by cochlear injury. Our results suggest that sustained patterns of noise-driven activity may prevent the injury-induced changes in central auditory processing that lead to this hyperactive state. From the perspective of laboratory studies of tinnitus, housing sound-exposed animals in uncontrolled noise levels may significantly reduce the success of induction procedures. From a broader clinical perspective, an early intervention with sound therapy may reduce the risk of tinnitus in individuals who have experienced an acute cochlear injury.
Keywordshyperactivity sound therapy hyperacusis
Support for this research was provided by the Tinnitus Research Consortium, Action on Hearing Loss, and NIDCD grant P30 DC005211. The authors thank ED Young and AM Lauer for their comments on a preliminary version of the manuscript.
Compliance with Ethical Standards
All procedures were reviewed and approved by the Institutional Animal Care and Use Committee of The Johns Hopkins University School of Medicine.
Conflict of Interest
The authors declare that they have no conflict of interest.
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