Magnetic stimulation of human peripheral nerve and brain: response enhancement by combined magnetoelectrical...

The authors describe the technique of magnetic stimulation from a pulsed induction coil (4.0 T) and the enhanced (5-fold) electromyogram response from hyperthenar muscles obtained when electric and magnetic stimuli are applied simultaneously. The enhancement results have been confirmed for central brain vertex stimulation using the Sheffield magnet. Results obtained with slow (1 to 6 seconds) depth electrode stimulation and recording in humans are compared and are used to predict probable developments in the magnetic field. Because magnetic and magnetoelectrical techniques are painless, noninvasive, and noninjurious, it is believed that they are an important advance in both research and clinical applications of instrumental modification of brain circuits and behavior. There are many diagnostic and therapeutic uses at peripheral and central levels, and some ethical problems need consideration.