Role of medial olivocochlear neural efferent pathway in perception of tinnitus in presence of silence

Over 20 million Americans struggle with troublesome effects of tinnitus. Tinnitus has a negative impact on a patient’s overall health and social well-being. Tinnitus can be a disabling condition. People with tinnitus regularly experience distress, depression, anxiety, sleep disturbances, frustration, poor concentration and in some cases pain. Currently, there are no scientifically validated cures available for most types of tinnitus. In fact, there is a deficiency in neurophysiological knowledge related to tinnitus. There is an informational gap between silence, which exacerbate or trigger tinnitus and Medial Oliovocochlear (MOC) efferent neural pathway connection. The primary aim of this study is to investigate the MOC efferent neural pathway and neural connections responsible for tinnitus generation in silence/sensory deprivation. The primary hypothesis of this study is that silence/sensory deprivation makes MOC efferent neural pathway hyperactive which participate in tinnitus perception. Method: fifty-eight normal hearing individuals between age 18-35 years were recruited as participants in this study. By placing normal hearing participants in a sound booth for 10 minutes, silence/sensory deprivation was created. This offered assessment of MOC neural pathway in normal hearing participants in silence. Hyperactivity of MOC neural pathway was assessed by its more suppressive effect on stimulated otoacoustic emissions (TEOAEs) in silence. The required auditory measurements were recorded in the sound booth using recommended diagnostic protocols to ensure the effect of “only silence” on auditory structures. Results: 41.4% of the participants perceived some type of tinnitus during/after 10 minutes of silence. Overall, Ringing was the most common type of tinnitus sound perception most participants who perceive tinnitus followed by “Cricket” and “Buzzing” sound. “Pulsating” or “Clear tone” sounds were less frequent followed by “Hissing,” “Ocean Roar,” and “Transformer.” No statistically significant difference was found in the total TEOAE and TEOAE suppression amplitude before and after 10 minutes of silence. Post silence total TEOAE suppression between tinnitus perceiving and non-perceiving tinnitus was not statistically significantly different. Conclusion: TEOAE generation is a peripheral phenomenon. Because tinnitus perception did not significantly change total TEOAE amplitude, the results may indicate higher central auditory structures as a source of tinnitus generation. Therefore, the results of the study support the notion that tinnitus is the central auditory processing phenomenon. The study may have failed to detect the changes in the medial olivocochlear efferent pathway because TEOAE tests might not be sensitive enough to detect the post silence changes in the pathway or top-down influence of the corticofugal pathway on lower auditory brainstem structures. This does not mean that medial olivocochlear efferent pathway does not participate in tinnitus perception. Results of the present study also seem to indicate that race may place a function in the perception of silence induced temporary tinnitus. Further investigation is needed to evaluate the functional contribution of the medial olivocochlear efferent pathway in tinnitus perception