Human brain mapping of tinnitus

Tinnitus is a phantom auditory perception that occurs in the absence of any external stimulus. Despite a long history of its known existence, few objective methods exist to confirm its presence and better understand the cortical disruptions that are assumed to underpin its perception. However, recent research has demonstrated the existence of an objective measure of tinnitus perception using resting and sound-evoked brain activity measured with magnetoencephalography (MEG). Significant differences have been found in individuals with tinnitus compared to those without. We aim to use similar methods of tinnitus measurement before, during, and after two tinnitus remediation programs to: (i) verify the results of previous studies; and (ii) evaluate whether subjective changes in tinnitus perception during tinnitus remediation correlate with objective measurements. In the first study (Chapter 2) we have discussed the behavioural tests of tinnitus, participant selection criteria, and changes in behavioural reports of tinnitus during remediation. In the second study (Chapter 3) we have compared the spontaneous cortical activity of tinnitus subjects and non-tinnitus controls. The third study (Chapter 4) aimed to evaluate tinnitus treatment-related changes in spontaneous cortical activity and their correlations with changes in objective reports of tinnitus. The fourth study (Chapter 5) looked at the relationship between evoked and spontaneous cortical activity in tinnitus participants and evaluated the effect of treatment on both. There was a significant difference in the spontaneous cortical activity of tinnitus participants and controls, these changes did not completely return to normalcy during the treatment phase. Some indications of treatment-related changes, however, were observed in the evoked responses. From the present experiment, we hypothesise that while spontaneous cortical activity can be used to identify the presence of tinnitus, evoked results could provide a more accurate representation of the benefits of a treatment program.