Force-loaded voluntary movement in MEG and DC-EEG/normal subject/neurological patients

In this proposal we intend to investigate, how movement-related cerebral magnetic fields (MEG, Bereitschaftsfeld, BF, Deecke et al. 1982a,b; 1983, Weinberg et al. 1983) behave as compared to movement-related cerebral potentials (DC-EEG) when the voluntary movements are loaded by force in comparison to unloaded movements. In previous experiments, the electroencephalographic basis of cortical organization of voluntary movement upon force-loading has been studied (Cui et al. 1996). This time the superior localization properties of magnetoencephalography (MEG) will be utilized, in order to clarify, which brain areas are involved in voluntary movement physiology and pathology upon force compensation and its mechanisms of adaptation. From behavioral studies, i.e. studying peripheral parameters we know that healthy man is able to rapidly adapt to varying force or resistence requirements. Not investigated in these studies was the question, in which brain areas such mechanisms of compensation do occur. It is, therefore, the aim of the present research project to investigate the cortical loci of such compensation. Force-adaptive action involves many features of everyday movements. All what we actively do against varying forces requires such adaptation. In addition, the inclusion of studies on patients with lesions of specific motor subsystems into the study is important, in order to find out where force-adaptive action does occur (i.e. the rapid compensatory adaptation against varying force-loading, from afferent information of position and motion receptors, muscle spindles, etc. in the periphery, especially regarding our psychophysical ability known as `sense of force` or `sense of weight`), and how force-adaptive action is disturbed by lesions of specific motor subsystems. Better understanding of these mechanisms would be of advantage for clinical-neurologic diagnostics and therapy (especially physiotherapy).

From the results of the project P12515 Force-loaded Voluntary Movement in MEG and DC-EEG/Normal Sub- jects/Neurol. Patients we can conclude that the supplementary motor area (SMA) and the cingulate motor area (CMA) are of great importance for our voluntary self-initiated movements. This knowledge, however, is not really widely distributed in public. Even among specialists it is insufficiently known, because the primary mo-tor area (MI) described by Foerster 1936 and Penfield 1960 with its homunculus is overestimated in the text-books. The importance of the supplementary motor area and the cingulate motor area is, however, at least as great as that of the primary motor area. It is true that lesions of primary motor area cause clinical disorders of immediate evidence (hemiparesis). The neurological signs after unilateral SMA lesion, as we have investigated, are more subtle. As with most frontal brain damage, unilateral SMA lesions are well compensated because the other side takes over with this function. If simple movements are investigated there are no obvious differences. However, if more complex movements are investigated in particular those who require temporal and spatial coordination of the two hands, one sees characteristic differences even with unilateral SMA lesions which we termed motor dysrhythmia or dyschronikinesia. Bilateral SMA lesions are disastrous for the patient. The re-sulting syndrome is called "loss of drive with preserved exitability from outside." This means that the patients lack their spontaneity and are only reflex machines. Fortunately, bilateral SMA lesions are more rare then uni-lateral once. Yet these results are of great importance for neurological therapy including restaurative functions, physiotherapy in short the complex of what is called `restaurative neurology.` The essential result of this proj-ect in one sentence reads: When it comes to the adjustment of varying forces in voluntary movement physiol-ogy, the SMA is of essential importance.