Surgically-induced unilateral deafness in adult humans: a unique opportunity to reveal neural basis of tinnitus

Tinnitus, the perception of sound in the absence of a physical source, is a common chronic hearing-related condition. Our epidemiological studies have revealed that tinnitus affects 10% of the UK adult population. Tinnitus is strongly associated with hearing loss, and seriously affects the quality of life of around 3-5% of the adult population. There is no cure for tinnitus. Therapeutic interventions are restricted to management of the symptoms and the subsequent distress. The evidence base for the efficacy of any of these therapeutic approaches is limited. There is a consensus that hearing loss results in hyperactivity in the central auditory system and this causes tinnitus. The development of individualised care for tinnitus patients (and ultimately a cure) requires a better understanding of the underlying mechanisms of tinnitus, along with more accurate ways to assess treatment efficacy. Therefore, the aim of this project is to investigate the neural mechanisms of tinnitus in adult humans.

The project will use patients with an acoustic neuroma (AN), a benign tumour that affects the auditory nerve. Surgery results in a sudden and profound hearing loss on the affected side. Our studies in this population have revealed large scale neuroplasticity and, importantly, around 50% of these patients report new tinnitus post-operatively. We will use a variety of psychophysical, electrophysiological and MRI tests before and after surgery to investigate the nature, and time course, of changes in neural activity, its amplitude and localization, and the presence of tinnitus. Brainstem and cortical EEG will be used cross-sectionally and longitudinally to measure activation at high temporal resolution. Pre- and post-surgery MRI, a novel tool in our studies of AN surgery, will localise longer-term plasticity using network analysis. Standard questionnaire and behavioral tests will characterise the tinnitus. We will also investigate factors (e.g., personality traits, attentional tuning etc) that might indicate a predisposition to tinnitus.

The student will receive: (i) general training in basic and translational research methodologies, and (ii) specific training in audiological, psychoacoustical, electrophysiological and MRI techniques. Our state-of-the-art research and clinical team, environment and track record of research on this population, mean we are well placed to successfully undertake the proposed work. The results of the project will provide a better understanding of the neural basis of tinnitus, and contribute to personalised treatment and improved outcomes.

www.psych-sci.manchester.ac.uk/audiologyanddeafness