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Open Access Highly Accessed Research article

Changes in motor cortex excitability associated with temporal repetitive transcranial magnetic stimulation in tinnitus: hints for cross-modal plasticity?

Martin Schecklmann1*, Michael Landgrebe4, Tobias Kleinjung3, Elmar Frank1, Philipp G Sand1, Rainer Rupprecht1, Peter Eichhammer1, Göran Hajak2 and Berthold Langguth1

Author Affiliations

1 Department of Psychiatry and Psychotherapy, University Regensburg, Universitätsstraße 84, 93053 Regensburg, Germany

2 Department of Psychiatry, Psychosomatic Medicine and Psychotherapy, Social Foundation Bamberg, Bamberg, Germany

3 Department of Otorhinolaryngology, University of Zurich, Zurich, Switzerland

4 Department of Psychiatry, Psychosomatics and Psychotherapy, kbo-Lech-Mangfall-Klinik, Agatharied, Germany

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BMC Neuroscience 2014, 15:71  doi:10.1186/1471-2202-15-71

Published: 4 June 2014

Abstract

Background

Motor cortex excitability was found to be changed after repetitive transcranial magnetic stimulation (rTMS) of the temporal cortex highlighting the occurrence of cross-modal plasticity in non-invasive brain stimulation. Here, we investigated the effects of temporal low-frequency rTMS on motor cortex plasticity in a large sample of tinnitus patients. In 116 patients with chronic tinnitus different parameters of cortical excitability were assessed before and after ten rTMS treatment sessions. Patients received one of three different protocols all including 1 Hz rTMS over the left temporal cortex. Treatment response was defined as improvement by at least five points in the tinnitus questionnaire (TQ). Variables of interest were resting motor threshold (RMT), short-interval intra-cortical inhibition (SICI), intracortical facilitation (ICF), and cortical silent period (CSP).

Results

After rTMS treatment RMT was decreased by about 1% of stimulator output near-significantly in the whole group of patients. SICI was associated with significant changes with respect to treatment response. The group of treatment responders showed a decrease of SICI over the course of treatment, the group of non-responders the reverse pattern.

Conclusions

Minor RMT changes during rTMS treatment do not necessarily suggest the need for systematic re-examination of the RMT for safety and efficacy issues. Treatment response to rTMS was shown to be related to changes in SICI that might reflect modulation of GABAergic mechanisms directly or indirectly related to rTMS treatment effects.

Keywords:
Transcranial magnetic stimulation; Motor cortex excitability; Motor cortex plasticity; Tinnitus; Cross-modal plasticity; Cortical silent period; Motor threshold; Intracortical inhibition; Intracortical facilitation