This chapter examines clinical motor mapping with magnetoencephalography (MEG). Motor cortex functional mapping procedures were first conducted by neurosurgeons who famously stimulated their patient’s exposed brain during surgery and then systematically documented the responses observed from the activated muscles of the body. Numerous neuroimaging-based functional mapping techniques followed, such as functional magnetic resonance imaging (fMRI), transcranial magnetic stimulation (TMS), high-density electroencephalography (HD-EEG), and MEG, which are currently used to map the motor areas in relation to isolated volitional movements. The use of MEG for presurgical functional mapping has become a standard component of clinical MEG practice. Indeed, knowledge regarding the location of eloquent MEG motor representations is valuable for presurgical planning and can improve outcomes by limiting the production of postsurgical deficits of motor function. Meanwhile, source localization challenges using equivalent current dipole (ECD) models have given way to newer methods, such as beamformer spatial filters, which have been validated clinically using electrical stimulation. It should also be noted that it is becoming increasingly evident that motor cortical oscillations are changing consistently over the life span, and thus consideration of the patient’s age will likely aid the interpretation of results.
Broadband source localization in a shallow‐water environment with a small bottom slope
