Cortico-muscular synchronization during isometric muscle contraction in humans as revealed by magnetoencephalography

Citation
J. Gross et al., Cortico-muscular synchronization during isometric muscle contraction in humans as revealed by magnetoencephalography, J PHYSL LON, 527(3), 2000, pp. 623-631
Citations number
43
Categorie Soggetti
Physiology
Journal title
JOURNAL OF PHYSIOLOGY-LONDON
ISSN journal
00223751 → ACNP
Volume
527
Issue
3
Year of publication
2000
Pages
623 - 631
Database
ISI
SICI code
0022-3751(20000915)527:3<623:CSDIMC>2.0.ZU;2-6
Abstract
1. Magnetoencephalographic (MEG) and electromyographic (EMG;) signals were recorded from six subjects during isometric contraction of four different m uscles. 2. Cortical sources were located from the MEG signal which was averaged tim elocked to the onset of motor unit potentials. A spatial filtering algorith m was used to estimate the source activity. Sources were found in the prima ry motor cortex (M1) contralateral to the contracted muscle. Significant co herence between rectified EMG and M1 activity was seen in the 20 Hz frequen cy range in all subjects. 3. Interactions between the motor cortex and spinal motoneuron pool were in vestigated by separately studying the non-stationary phase and amplitude dy namics of M1 and EMG signals. 4. Delays: between M1 and EMG signals, computed from their phase difference , were found to be in agreement with conduction times from the primary moto r cortex to the respective muscle. The time-dependent cortico-muscular phas e synchronization was found to be correlated with the time course of both M 1 and EMG signals. 5. The findings demonstrate that the coupling between the primary motor cor tex and motoneuron pool is at least partly due to phase synchronization of 20 Hz oscillations which varies over time. Furthermore, the consistent phas e lag between M1 and EMG signals, compatible with conduction time between M 1 and the respective muscle with the M1 activity preceding EMG activity, su pports the conjecture that the motor cortex drives the motoneuron pool.