Dynamic synchronisation of central oscillators in essential tremor

• Published in: Clinical neurophysiology 2003-08, Vol.114 (8), p.1462-1467
• Main Authors: Hellwig, B, Schelter, B, Guschlbauer, B, Timmer, J, Lücking, C.H
• Format: Article
• Language: English
• Subjects: Adult; Aged; Biological and medical sciences; Brain Mapping; Cortical Synchronization - methods; EEG-EMG coherence; Electrodes; Electrodiagnosis. Electric activity recording; Electromyography - methods; Essential tremor; Essential Tremor - physiopathology; Female; Functional Laterality; Humans; Interhemispheric interaction; Investigative techniques, diagnostic techniques (general aspects); Male; Medical sciences; Middle Aged; Motor cortex; Muscle Contraction - physiology; Nervous system; Neural Conduction; Oscillation; Somatosensory Cortex - physiology; Wrist - physiology
• ISSN: 1388-2457; 1872-8952
• DOI: 10.1016/S1388-2457(03)00116-0

Objective: Coherence analysis of electromyography (EMG) signals in essential tremor (ET) suggests that tremor in the right and left arm is induced by independent central oscillators. The sensorimotor cortex seems to be part of the tremor-generating neuronal network in ET. Here, we investigated using electroencephalography (EEG) whether the independence of central oscillators in ET is supported by the analysis of cortical activity. Methods: In 8 patients with ET, bilateral hand tremor was activated by wrist extension. EMGs from the wrist flexors and extensors were recorded simultaneously with an EEG. EEG-EMG coherence was estimated for 74 epochs of 60 s duration. Results: In 42.6% of the cases, EEG-EMG coherence at the tremor frequency existed only with the contralateral sensorimotor cortex. However, 21.6% of the tremor-EMGs were coherent with EEG activity over both the contralateral and ipsilateral sensorimotor cortex. Bilateral and exclusively contralateral EEG-EMG coherence could alternate within the same recording. Bilateral EEG-EMG coherence was associated with increased right-left EEG-EEG coherence, increased right-left EMG-EMG coherence as well as with increased tremor strength. Conclusions: In ET, central oscillators in the right and left brain are not entirely independent of each other. They may dynamically synchronise, presumably by interhemispheric coupling via the corpus callosum.