The Central Oscillatory Network of Essential Tremor
ABSTRACT The responsible pathological mechanisms of essential tremor are not yet clear. In order to understand the mechanisms of the central network its sources need to be found. The cortical sources of both the basic and first "harmonic" frequency of essential tremor are addressed in this paper. The power and coherence were estimated using the multitaper method for EEG and EMG data from 6 essential tremor patients. The Dynamic Imaging of Coherent Sources (DICS) was used to find the coherent sources in the brain. Before hand this method was validated for the application of finding multiple sources for the same oscillation in the brain by using two model simulations which indicated the accuracy of the method. In all the essential tremor patients the corticomuscular coherence was also present in the basic and the first harmonic frequency of the tremor. The source for the basic frequency and the first harmonic frequency was in the region of primary sensory motor cortex, prefrontal and in the diencephalon on the contralateral side for all the patients. Thus the generation of these two oscillations involves the same cortical areas and indicates the oscillation at double the tremor frequency is a harmonic of the basic tremor frequency.
- SourceAvailable from: Pedro Montoya[Show abstract] [Hide abstract]
ABSTRACT: The purpose of the study was to analyze corticomuscular coherence during planning and execution of simple hand movements in individuals with cerebral palsy (CP) and healthy controls (HC). Fourteen individuals with CP and 15 HC performed voluntary paced movements (opening and closing the fist) in response to a warning signal. Simultaneous scalp EEG and surface EMG of extensor carpi radialis brevis were recorded during 15 isotonic contractions. Time-frequency corticomuscular coherence (EMG-C3/C4) before and during muscular contraction, as well as EMG intensity, onset latency and duration were analyzed. Although EMG intensity was similar in both groups, individuals with CP exhibited longer onset latency and increased duration of the muscular contraction than HC. CP also showed higher corticomuscular coherence in beta EEG band during both planning and execution of muscular contraction, as well as lower corticomuscular coherence in gamma EEG band at the beginning of the contraction as compared with HC. In conclusion, our results suggest that individuals with CP are characterized by an altered functional coupling between primary motor cortex and effector muscles during planning and execution of isotonic contractions. In addition, the usefulness of corticomuscular coherence as a research tool for exploring deficits in motor central processing in persons with early brain damage is discussed.Journal of Electromyography and Kinesiology 07/2014; DOI:10.1016/j.jelekin.2014.07.004 · 1.73 Impact Factor
Article: Dynamic imaging of coherent sources[Show abstract] [Hide abstract]
ABSTRACT: Electric source imaging allows localization of sources in the brain underlying frequency-associated EEG patterns detected on the scalp EEG. New algorithms have substantially improved the localization power of the EEG. Dynamic imaging of coherent sources (DICS) is one of these solutions. This algorithm uses a spatial filter to map power and coherence estimates of oscillatory brain activity. In this focus article, we explain the DICS method and summarize studies representing the ability of DICS to detect cortical and subcortical electric sources and neuronal networks associated with absence seizures, photoparoxysmal responses and hypsarrhythmia. By applying renormalized partial directed coherence (RPDC), the information flow between 2 sources can be described, which contributes to a better understanding of networks underlying different forms of epilepsy.Zeitschrift für Epileptologie 02/2013; 26(1). DOI:10.1007/s10309-012-0292-0
- [Show abstract] [Hide abstract]
ABSTRACT: Parkinsonian tremor (PD), essential tremor (ET) and voluntarily mimicked tremor represent fundamentally different motor phenomena, yet, magnetoencephalographic and imaging data suggest their origin in the same motor centers of the brain. Using EEG-EMG coherence and coherent source analysis we found a different pattern of corticomuscular delays, time courses and central representations for the basic and double tremor frequencies typical for PD suggesting a wider range defective oscillatory activity. For the basic tremor frequency similar central representations in primary sensorimotor, prefrontal/premotor and diencephalic (e.g. thalamic) areas were reproduced for all three tremors. But renormalized partial directed coherence of the spatially filtered (source) signals revealed a mainly unidirectional flow of information from the diencephalon to cortex in voluntary tremor, e.g. a thalamocortical relay, as opposed to a bidirectional subcortico-cortical flow in PD and ET promoting uncontrollable, e.g. thalamocortical, loop oscillations. Our results help to understand why pathological tremors although originating from the physiological motor network are not under voluntary control and they may contribute to the solution of the puzzle why high frequency thalamic stimulation has a selective effect on pathological tremor leaving voluntary movement performance almost unaltered.NeuroImage 01/2012; 60(2):1331-9. DOI:10.1016/j.neuroimage.2012.01.088 · 6.13 Impact Factor