Magnetic Stimulation of Neural Tissue: Techniques and System Design

Abstract

Magnetic stimulation of neural tissue is an attractive technology because neural excitation may be affected without the implantation of electrodes. This chapter provides a brief overview of the technology and relevant literature. While extensive magnetic stimulation modeling and clinical experimentation work has been presented, considerably less quantitative in vitro work has been performed. In vitro experiments are critical for characterizing the site of action, the structures stimulated, and the long-term tissue histological effects. In vitro systems may also facilitate the development of novel magnetic stimulation approaches. To demystify magnetic stimulation systems, this chapter presents an in vitro experimental system using a systematic design methodology. The modeling methods are designed to aid experimentation. Circuit schematics, test rigs, and supplier information are given to support practical implementation of this design methodology. Example neural preparations and their modeling and use are also covered. Finally, as an alternative to pulsed discharge circuits for magnetic stimulation, this chapter shows how to use a circuit to deliver asymmetric current pulses to generate the magnetic field.

A theoretical framework for studying the electromagnetic stimulation of nervous tissue

“…The model was also used to evaluate the electric fields and their spatial derivatives for different geometries, namely the round, figure-eight, concentric, as well as square coils. The electric fields computed using the model are in good agreement with those previously published [11][12] [14]. The current ramp used in this paper for all coils geometries was 5A/µs, an arbitrary value adopted for exemplification purposes.…”

Selective stimulation of rat sciatic nerve using an array of mm‐size magnetic coils: a simulation study

“…The coil‐winding axis is parallel to either the y ‐axis (coils 2 and 4) or z ‐axis (coils 1 and 3), and is located in the plane of the x ‐axis mid‐point of the nerve. The coil‐winding axis of each coil is offset from the centre of the nerve so as to place the mid‐point between the inner and outer diameters of the coil closest to the nerve, which results in the largest induced electric field occurring in the nerve (explained in the Section 3) [15]. The minimum distance between each coil and the nerve is 0.5 mm.…”

Design and optimization of microscale magnetic probes for multi-site neural stimulation

“…The closed-form expression of @' ë @T ¤ generated by a square microcoil is determined by Eq. (1) [15], where N is the turn number of the coil, ä 4 is the permeability of vacuum, @E @P ¤ is the current ramping rate, and a is the length of the square coil.…”