TRI Neurostimulation Workgroup
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TRI Neurostimulation Workgroup
Today, it is thought that tinnitus is the result of maladaptive neuroplasticity leading to reorganization of the auditory system all the way up to the auditory cortex. Ultimately, an aberrant neural signal within the cortex will cause an auditory perception. The task of the TRI neurostimulation workgroup is double: looking for the neural correlates of tinnitus and understanding further the mechanisms of tinnitus, and try to find means for interfering with the aberrant neural activity causing tinnitus and with the neural network responsible for the distress associated to tinnitus.
The workgroup therefore consists of neurobiologist (Arnaud Norena), MEG specialist (Nathan Weisz, Winny Schlee), imaging data processing specialist (Marco Congedo), neuroscientist (Sven Vanneste), ENT specialist (Alain Londero), neurologist/psychiatrist (Berthold Langguth) and a neurosurgeon (Dirk De Ridder). In order to achieve its mission this workgroup tries to combine the philosophy of the exploration with neuroscientific methodology.
Every 3 to 4 months the workgroup members meet to discuss the recent progress of their studies and to meet with invited eminent neuroscientists.
Neuromodulation methods used by the workgroup are transcranial magnetic stimulation, transcranial direct currents stimulation, neurobiofeedback and implantation of electrodes in the brain, and neuroimaging techniques used to unravel the brain mechanisms involved consist of EEG, MEG and fMRI.
It was initially thought that the auditory cortex aberrant activity would be the final common pathway of tinnitus perception and that modifying or normalizing this activity would eliminate tinnitus in everybody. It is not known why rTMS and implanted electrodes on the auditory cortex do not benefit everybody, but it is a scientifically very important question that has wider repercussions than just tinnitus. It goes back to fundamental questions of the function of the primary, secondary and association cortices, and what is needed as minimal neural activity to develop a conscious percept. But this fact can also be used as an extra approach to study tinnitus. The neurostimulation workgroup therefore also looks at other basic and clinical neuroscientists to fulfil its mission. For example brilliant work performed by the coma science group in Liège, Belgium has shown that isolated auditory cortex activity is not sufficient for conscious auditory perception, which fits with the global workspace theory that suggests primary sensory cortex activity needs to be co-active with other brain areas for conscious perception to arise. Therefore some ideas of why auditory cortex stimulation does not benefit everybody could be: 1. The auditory cortex is not important in chronic tinnitus, but other yet incompletely defined areas are, 2. Mirror activity in the ipsi/contalateral cortex develops in time, 3. Allostatic mechanisms prevent normalization of auditory cortex activity, 4. Wrong stimulation designs are being applied, etc.
Depending on what future MEG, EEG, fMRI and PET studies will reveal will new neurostimulation strategies be developed.
Auditory cortex stimulation is only one of the options for tinnitus suppression. Even though some patients are markedly improved, and some tinnitus-free, not all patients implanted benefit from the stimulation. New targets will be implanted in the near future, and non-invasive neuromodulation will be diversified: transcranial magnetic stimulations are being applied at multiple areas in different combinations and new neurobiofeedback protocols are being developed, based on sLORETA and connectivity analyses.
The very dynamic neurostomulation workgroup is there for the benefit of all people with tinnitus and for all who are interested in how the brain works.