title: Unilateral tinnitus: changes in connectivity and response lateralization measured with FMRI.
abstract: Tinnitus is a percept of sound that is not related to an acoustic source outside the body. For many forms of tinnitus, mechanisms in the central nervous system are believed to play a role in the pathology. In this work we specifically assessed possible neural correlates of unilateral tinnitus. Functional magnetic resonance imaging (fMRI) was used to investigate differences in sound-evoked neural activity between controls, subjects with left-sided tinnitus, and subjects with right-sided tinnitus. We assessed connectivity patterns between auditory nuclei and the lateralization of the sound-evoked responses. Interestingly, these response characteristics did not relate to the laterality of tinnitus. The lateralization for left- or right ear stimuli, as expressed in a lateralization index, was considerably smaller in subjects with tinnitus compared to that in controls, reaching significance in the right primary auditory cortex (PAC) and the right inferior colliculus (IC). Reduced functional connectivity between the brainstem and the cortex was observed in subjects with tinnitus. These differences are consistent with two existing models that relate tinnitus to i) changes in the corticothalamic feedback loops or ii) reduced inhibitory effectiveness between the limbic system and the thalamus. The vermis of the cerebellum also responded to monaural sound in subjects with unilateral tinnitus. In contrast, no cerebellar response was observed in control subjects. This suggests the involvement of the vermis of the cerebellum in unilateral tinnitus.
authors.affiliation: Department of Otorhinolaryngology/Head and Neck Surgery, University Medical Center Groningen, University of Groningen, Groningen, Netherlands; Graduate School of Medical Sciences (Research School of Behavioural and Cognitive Neurosciences), University of Groningen, Groningen, Netherlands.
authors.forename: Cornelis P
authors.initials: CP
authors.lastname: Lanting
authors.affiliation: Department of Otorhinolaryngology/Head and Neck Surgery, University Medical Center Groningen, University of Groningen, Groningen, Netherlands; Graduate School of Medical Sciences (Research School of Behavioural and Cognitive Neurosciences), University of Groningen, Groningen, Netherlands.
authors.forename: Emile
authors.initials: E
authors.lastname: de Kleine
authors.affiliation: Department of Otorhinolaryngology/Head and Neck Surgery, University Medical Center Groningen, University of Groningen, Groningen, Netherlands; National Institute for Health Research, Nottingham Hearing Biomedical Research Unit, School of Clinical Sciences, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom.
authors.forename: Dave R M
authors.initials: DR
authors.lastname: Langers
authors.affiliation: Department of Otorhinolaryngology/Head and Neck Surgery, University Medical Center Groningen, University of Groningen, Groningen, Netherlands; Graduate School of Medical Sciences (Research School of Behavioural and Cognitive Neurosciences), University of Groningen, Groningen, Netherlands.
authors.forename: Pim
authors.initials: P
authors.lastname: van Dijk
mesh_terms: D000328:Adult; D000368:Aged; D001303:Auditory Cortex / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D001933:Brain Stem / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011859:Radiography; D014012:Tinnitus