Annals of biomedical engineering
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We determined the location of excitation for different positions of a round and butterfly coil during in vitro magnetic stimulation of cut peripheral nerves. We analyzed the conditions under which excitation occurs, either at the termination or at the peak of the field gradients (first spatial derivative of the electric field). ⋯ Excitation occurred at the negative peak of the field gradients along a nerve when 1) a coil was positioned far away from the ends of a nerve, 2) there were no geometric or volume conductor inhomogeneities around a nerve, and 3) it was of sufficient magnitude. Threshold strengths for excitation at terminations were significantly lower than that for field gradient excitation and comparable to that due to geometric and volume conductor inhomogeneities.