MEASUREMENT OF THE ACTIVATING FUNCTION OF MAGNETIC STIMULATION USING COMBINED ELECTRICAL AND MAGNETIC STIMULI

The technique of combined magnetic and electrical stimulation of a per ipheral nerve was used to determine the effectiveness of the combined stimulus and its dependence on the relative positioning of electrodes and stimulator coil along the axis of the nerve. The results were used to determine the magnetic stimulation-activating function of a long, straight nerve in the arm, and are shown to be consistent with publish ed theoretical models constructed under conditions of simplified tissu e geometry. With appropriate positioning of the two stimulators and si milar tissue current waveforms, both enhancement and inhibition of an electrical stimulus were demonstrated and the maximum amplitude of the combined stimulus approached the arithmetic sum of that produced by e ach stimulator individually.