Abstract
A method of localized stimulation of the human brain is proposed. The basic idea is to concentrate induced eddy currents locally in the vicinity of a target by a pair of opposing pulsed magnetic fields. A pair of coils are positioned outside the head so that time-varying magnetic fields pass through the head in the opposite directions around a target. The eddy currents induced at the target are expected to flow together, which results in an increased current flow at the target. The current density at the target makes a peak which is higher by 2-3 times than current densities at non-target regions. Based upon the computer simulation, a figure eight coil was designed, and the magnetic brain stimulation was carried out using the authors as volunteers. The results showed that the selective stimulation of the brain was achieved within a 5 mm resolution. The functional mapping of the human motor cortex related to the hand, arm and foot area was obtained. It was also observed that the optimum direction of stimulating currents for neural excitation exists in each functional area in the cortex. The localization of the target area was confirmed by magnetic resonance imaging.
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