ABSTRACT
In 1980, Merton and Morton –rst reported muscle responses in an unanesthetized human following motor cortex stimulation with high-voltage electric shocks delivered through the intact skull. Although noninvasive, this high-intensity transcranial electrical stimulation (TES) is painful because of activation of pain –bers in the scalp. In 1985, Barker et al. showed that painless transcranial stimulation of the human brain could be obtained using the small electric –eld induced by a timevarying magnetic –eld, which in turn is produced by passing a large current through an insulated copper wire coil placed above the scalp. As magnetic –eld is not signi–- cantly attenuated by the scalp and skull, the induced electric current could activate super–cial neural elements (Roth et al., 1991).
