ANIMAL MAGNETISM: Light shone into one eye of an anesthetized cat stimulates electrical activity in the visual cortex. A magnetrode (green) inserted less than a millimeter into the visual cortex detects the magnetic fields created by this electrical activity. Insertion of an electrode adjacent to the magnetrode allows researchers to gather and compare electrical current and magnetic field data at the same time.© GEORGE RETSECK
The brain is often described in terms of its wiring, connections, and circuits, and such language is not merely an analogy to a building’s electrical infrastructure. Neurons control the flow of charged ions—receiving, perpetuating, and discharging currents—to perform their essential functions.
Analyzing the brain’s electrical activity to gain insights into its function can be achieved with electrodes either placed upon the scalp—as in electroencephalograms (EEGs)—or inserted into the brain. But electrical currents also produce magnetic fields, and detecting these fields can offer several advantages over voltage measurements, says Myriam Pannetier-Lecoeur of the French Alternative Energies and Atomic Energy Commission.
For example, while electrical fields and voltage measurements are distorted by the insulating or conductive properties of surrounding tissues, magnetic fields are not. Furthermore, electrodes are ...
