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Major project: Structural Changes in Tinnitus Patients and Their Relationship to Hearing-Loss

Blecourt, C. M. de and Koops, E. A. and Dijk, P. van (2016) Major project: Structural Changes in Tinnitus Patients and Their Relationship to Hearing-Loss. Master's Thesis / Essay, Behavioural and Cognitive Neurosciences.

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Subjective tinnitus is the perception of sound without an external source. Tinnitus is highly associated with hearing-loss, but theories that attempt to explain tinnitus rarely consider hearing-loss as a cofounding variable. Leaver et al. (2011) propose that a gating mechanism is unable to properly inhibit the unwanted tinnitus signal. The key areas of this theory, amygdala and ventromedial prefrontal cortex, usually show less grey matter (GM) than controls. Perhaps a lack of GM prevents the gating system to correctly inhibit the tinnitus signal. Theories on tinnitus involve a mismatch in the functional reorganisation in several brain areas, especially the auditory cortex (Jastreboff, 1990). Structural studies often assume that the functional reorganisation is accompanied by structural reorganisation. Volumetric studies on tinnitus often find differences in the auditory, limbic, and frontal areas between tinnitus patients and controls. This study compared anatomical MRI-scans of 23 tinnitus patients with 4 individuals with hearing-loss and 6 healthy controls. Tinnitus and control subjects have on average more grey matter in the left superior temporal cortex than hearing-impaired individuals. Region-of-Interest analysis showed that controls had more grey matter in the left parahippocampal cortex compared to tinnitus patients. Tinnitus patients had more grey matter than the hearing-loss group in auditory, limbic, and frontal areas. The findings suggest that hearing-loss group had the strongest decrease in GM volume in the limbic system. The tinnitus group is somewhere between the hearing-loss group and the controls. The findings suggest that the limbic system is involved in the tinnitus percept, but it seems that the gating mechanism is not situated here. It might be that this gate is situated in the frontal cortex, but the frontal findings seem to be related to tinnitus distress. Structural reorganisation is possibly the strongest in hearing-impaired individuals, and only partially happening in tinnitus patients, suggesting that reorganisation may not have happened properly. It is emphasised that the sample group size and hearing-levels are not ideal, and tinnitus distress should be taken into account in further studies.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Behavioural and Cognitive Neurosciences
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 08:24
Last Modified: 15 Feb 2018 08:24

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