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Electroencephalographic and magnetoencephalographic studies of motor function
H Weinberg1, D Cheyne, D Crisp
1Department of Psychology, Simon Fraser University, Burnaby, British Columbia, Canada.
Advances in Neurology
|January 1, 1990
Summary
Magnetoencephalography (MEG) reveals bilateral brain activity before voluntary movement, challenging previous EEG findings. MEG also identifies sensorimotor cortex sources for movement-evoked fields, offering new insights into motor control.
Area of Science:
- Neuroscience
- Motor Control
- Brain Imaging
Background:
- Scalp-recorded electroencephalography (EEG) has limitations in spatial resolution, obscuring the precise origins of movement-related potentials.
- Magnetoencephalography (MEG) and source localization offer improved methods for studying human cortical activation during movement.
Purpose of the Study:
- To investigate the cortical sources of movement-related potentials using MEG.
- To compare MEG findings with existing EEG data on motor control.
Main Methods:
- Analysis of movement-related magnetic fields recorded using MEG.
- Application of source localization techniques to neuromagnetic recordings.
- Comparison of MEG data with electroencephalography (EEG) findings.
Main Results:
- Slow "readiness" magnetic fields detected prior to voluntary movement indicate bilateral sensorimotor cortex activation, starting as early as 0.5 seconds before the movement.
- A significant "movement-evoked field" at approximately 110 msec post-EMG onset suggests a contralateral sensorimotor dipolar source, likely representing early reafferent input.
- Individual variability in movement-evoked fields, more pronounced in MEG than EEG, may stem from multiple overlapping sources in the sensorimotor cortex.
Conclusions:
- MEG provides a promising noninvasive approach to studying cortical motor function.
- The assumption of purely contralateral sources for readiness potentials, based on EEG, needs reevaluation.
- MEG can potentially resolve complex sensorimotor activity by analyzing temporal overlaps of pre-movement and movement-evoked signals.