Biomagnetism

Abstract

The electrical activity of nerves and muscle produces small magnetic fields: biomagnetism. We analyze the magnetic field produced by a single nerve fiber, and develop a current-dipole model for this magnetic field when measured far away. Electrical activity in the heart gives rise to the magnetocardiogram, and electrical activity in the brain causes the magnetoencephalogram. This chapter then explores electromagnetic induction and transcranial magnetic stimulation of the brain. An understanding of magnetic materials is needed to describe magnetotactic bacteria. The chapter ends with a discussion of the detection of weak magnetic fields using a superconducting quantum interference device (SQUID) magnetometer.