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Dynamic synchronisation of central oscillators in essential tremor
B Hellwig1, B Schelter, B Guschlbauer
1Neurologische Universitätsklinik, Neurozentrum, Breisacher Strasse 64, 79106 Freiburg, Germany. hellwigb@nz.ukl.uni-freiburg.de
Summary
Central oscillators in essential tremor (ET) are not fully independent. Brain activity in the right and left hemispheres can synchronize, suggesting interhemispheric coupling contributes to tremor generation.
Area of Science:
- Neuroscience
- Biomedical Engineering
Background:
- Essential tremor (ET) is characterized by involuntary rhythmic shaking.
- Previous electromyography (EMG) analysis suggested independent central oscillators for right and left arm tremors in ET.
- The sensorimotor cortex is implicated in the neuronal network generating ET.
Purpose of the Study:
- To investigate if electroencephalography (EEG) analysis supports the independence of central oscillators in ET.
- To examine the relationship between cortical activity and tremor generation in ET patients.
Main Methods:
- Simultaneous recording of EMG from wrist flexors and extensors with EEG in 8 ET patients.
- Bilateral hand tremor was induced by wrist extension.
- EEG-EMG coherence was calculated for 74 epochs of 60-second duration.
Main Results:
- EEG-EMG coherence at tremor frequency was observed with the contralateral sensorimotor cortex in 42.6% of cases.
- In 21.6% of cases, tremor-EMGs showed coherence with both contralateral and ipsilateral sensorimotor cortex EEG.
- Bilateral EEG-EMG coherence correlated with increased EEG-EEG coherence, EMG-EMG coherence, and tremor strength.
Conclusions:
- Central oscillators in the right and left brain hemispheres are not entirely independent in ET.
- Dynamic synchronization of these oscillators occurs, likely mediated by interhemispheric coupling via the corpus callosum.