Functional magnetic resonance imaging of tinnitus

Promotie: dhr. C.P. Lanting, 16.15 uur, Academiegebouw, Broerstraat 5, Groningen

Proefschrift: Functional magnetic resonance imaging of tinnitus

Promotor(s): prof.dr. P. van Dijk

Faculteit: Medische Wetenschappen

Contact: via de persvoorlichters van het UMCG, tel. 050-361 2200, e-mail: voorlichting bvl.umcg.nl

Functional magnetic resonance imaging of tinnitus

This thesis is aimed at a better understanding of the neural representation of tinnitus. A number of studies were performed in which fMRI was used to measure neural activity in the brain.

First, studies were performed in which the activity of different patient groups was compared with those of a control group. The level of sound-evoked responses was measured in auditory areas in the brain. In addition, we measured the response lateralization and the functional connectivity between areas in the brain. Both the lateralization and the patterns of connectivity seem disturbed in the auditory path of patients with tinnitus. The sound-evoked responses in the midbrain are elevated in some patients with tinnitus.

Second, we studied a phenomenon that in some patients jaw movement could modulate the loudness of the tinnitus. The effect of this jaw movement on the tinnitus and the corresponding neural activity was measured. In both controls as the patients, this jaw movement elicits activity in the auditory path. Differences between groups were observed in the brainstem. The results show that the modulation of tinnitus by jaw movement may be based on interaction between somatosensory and auditory input in the brain.

Finally, the white-matter tracts in the brain were studied. A path between the auditory system and the limbic system was shown and may explain the influence of tinnitus on the daily life of patients.

The experiments in this thesis show that there are subtle functional and structural differences between subjects with and without tinnitus.