Chapter 3 EEG (MEG)/EMG correlation

Abstract

The cerebral cortex is involved in the control of voluntary movements to various extents depending on the kind of movement. In involuntary movements such as myoclonus and dystonia, the sensori-motor cortex, in particular, is involved either directly or indirectly in the pathophysiology. The functional relation between the cortical activities and the movements, whether voluntary or involuntary, can be studied non-invasively by using the functional neuroimaging techniques such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET), and with various electrophysiological methods. Among the latter techniques, the simultaneous recording of electroencephalogram (EEG) or magnetoencephalogram (MEG) with electromyograms (EMG) provides useful information about the temporal and spatial relation among the cortical activities and those movements. Subcortical structures, especially basal ganglia and cerebellum, are extremely important for the control of voluntary motor execution and in relation to the pathogenesis of certain involuntary movements. By using EEG or MEG, however, the functional states of these subcortical structures can only be estimated by measuring the cortical activities that might be influenced by the functional abnormalities of these subcortical structures. Three kinds of electrophysiological methods can be used for analyzing the relation among the cortical electric activities and the movements: (1) recording of electric or magnetic fields associated with the movement; (2) analysis of change of cortical rhythmic oscillations related to the movement; and (3) coherence analysis between EEG or MEG and EMG.