Tinnitus affects 10-15% of the population and causes a diminished quality of life for 1-3% of people. Without a clear understanding of the mechanisms that generate and sustain tinnitus, treatment plans can only attempt to manage the problem rather than address the underlying causes of tinnitus. As 85% of tinnitus sufferers have hearing loss, tinnitus was originally considered to be a problem of the ear. Moreover the remaining tinnitus sufferers are postulated to have hidden hearing loss. Subsequent research has found that tinnitus is a problem extending beyond the ear. Experimental findings have identified tinnitus related activity throughout the auditory system. It is unclear how this activity is created and how it leads to the perception of a phantom sound. This thesis aims to identify the factors involved in the development of tinnitus related activity and the manifestation of a phantom sound; computational models of the auditory system are developed to address this primary objective. In this thesis, a biologically inspired model of the auditory periphery is created, called the peripheral model, which emulates tinnitus related activity in the auditory brainstem and accurately models hidden hearing loss in line with empirical data. The peripheral model is extended to model correlates of tinnitus associated with the thalamocortical network. Finally a perceptual model of tinnitus is developed using a Linear Mixed Effects (LME) approach to show how tinnitus related activity leads to the perception of a phantom sound. The outcomes from the development of the peripheral model include an accurate model of cochlear synaptopathy to replicate hidden hearing loss as well as the finding that hidden hearing loss can instigate adaptive changes that result in tinnitus related activity. Extending the peripheral model to include the thalamocortical network led to the discovery that tinnitus requires changes to both the bottom-up and top-down signals in the auditory system. The result provides a significant step forward towards understanding the mechanisms underpinning tinnitus related activity. The peripheral model and the result from the investigation of the thalamocortical network provide the underpinning basis upon which to develop the perceptual model of tinnitus using a LME approach. The LME model provides a state of the art perceptual model of tinnitus that accurately models characteristics of tinnitus such as pitch and loudness. The results provide a significant advancement in the understanding of tinnitus generation and the evidence to motivate and direct further studies, which could lead to improved treatment methods for this condition.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:730910 |
| Date | January 2017 |
| Creators | Gault, Richard |
| Publisher | Ulster University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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