Beta-Range EEG-EMG Coherence With Isometric Compensation for Increasing Modulated Low-Level Forces

Abstract

Chakarov V, Naranjo JR, Schulte-Mö nting J, Omlor W, Huethe F, Kristeva R. Beta-range EEG-EMG coherence with isometric compensation for increasing modulated low-level forces. J Neurophysiol 102: 1115-1120, 2009. First published May 20, 2009 doi:10.1152/jn.91095.2008. Corticomuscular synchronization has been shown to occur in beta (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) and gamma range (30 -45 Hz) during isometric compensation of static and dynamic (periodically modulated) low-level forces, respectively. However, it is still unknown to what extent these synchronization processes in beta and gamma range are modified with increasing modulated force. We addressed this question by investigating the corticomuscular coherence (CMC) between the electroencephalogram (EEG) and electromyogram (EMG) from the first dorsal interosseus muscle (FDI) as well as the cortical and muscular spectral power during a visuomotor task where different levels of a dynamic (modulated) force were used. Seven healthy right-handed female subjects compensated dynamic forces at 8, 16, and 24% of the maximal voluntary contraction (MVC) isometrically with their right index finger. Under the three conditions investigated, we found a broad-band CMC comprising both beta and gamma range and peaking at ϳ22 Hz within the beta band. This broad-band coherence increased linearly with higher force level. A separate analysis of the gamma range CMC did not show significant modulation of the CMC by the force levels. EEG and EMG spectral power did not show any significant difference among the three force conditions. Our results favor the view that the function of beta range CMC is not specific for low-level static forces only. The sensorimotor system may resort to stronger and also broader beta-range CMC to generate stable corticospinal interaction during increased force level, as well as when compensating for dynamic modulated forces. This finding re-enforces the importance of the beta-range EEG-EMG coherence in sensorimotor integration. I N T R O D U C T I O NMuch attention has been given to the functional organization of the corticospinal system and the mechanisms of muscle control by the CNS and in particular to the universal mechanism of neuronal interaction via synchronization, which plays a relevant role in the effective coordination between the cortical motor areas and the muscles. This synchronization mechanism can be described by the coherence function for different frequency ranges. During maintained motor contraction the cortical motor areas and the muscles are synchronized in beta-range as shown in monkeys (Baker et al. 1997(Baker et al. , 1999 Fetz 1992, 1996) (Perez et al. 2006). Based on the finding that increased beta-range CMC and better performance are correlated, we suggested the betarange CMC as a mechanism for effective corticospinal interaction during static forces .Because one of the main functions of the motor cortex is to control force output (Ashe 1997), modulation of the beta-range CMC by different stati...

Changes of cortico-muscular coherence: an early marker of healthy aging?

“…But, two pharmacological intervention studies suggest that CMC and M1 oscillations represent separate phenomena and strengthen the hypothesis that CMC reflects a significant mechanism rather than a simple transfer of an essential cortical phenomenon (Baker and Baker 2003;Riddle et al 2004). Secondly, CMC strength and frequency vary with force (Chakarov et al 2009;Witte et al 2007). At very low forces, (i.e., 4% of maximum voluntary contraction, MVC) CMC frequency is higher while CMC strength is lower as compared to weak forces (i.e., 16% of MVC; ).…”

Motor control differs for increasing and releasing force

“…Specifically, modulation of motor units between 0 and 4 Hz has been associated with common drive (De Luca and Erim 2002), and modulation between 4 and 10 Hz (theta and alpha bands) has been associated with working memory, short-term memory, and emotional arousal (Jensen and Lisman 2005;Knyazev 2007) and force control in tonic contraction (Mima et al 2000). Oscillations between 10 and 35 Hz have been linked with motor function and maintenance of a steady motor output (Chakarov et al 2009;Engel and Fries 2010) and precision in motor output (Kristeva-Feige et al 2002), and oscillations between 35 and 60 Hz have been associated with strong voluntary contractions (Brown et al 1998;Chakarov et al 2009). …”

EEG signatures of arm isometric exertions in preparation, planning and execution

“…There is considerable documented research about EEG correlates of isometric force generation or movement, but most of them approach the EEG or MEG signal from different viewpoints such as: corticomuscular coherence (Chakarov et al, 2009;Conway et al, 1995;Salenius and Hari, 2003;Schoffelen et al, 2008); reflection of arm (Siemionow et al, 2000), finger (Oda et al, 1996;Shibata et al, 1997;Slobounov et al, 2002) or foot (do Nascimento et al, 2005(do Nascimento et al, , 2006 force magnitude in MRPs; classifying force or rate of torque development in real or imaginary isometric tasks (Gu et al, 2009;do Nascimento and Farina, 2008;Romero et al, 2000). We now underline the reports more closely related to our study, i.e.…”