Biomagnetism: Magnetic Fields Produced by the Human Body

David Cohen, MIT

Friday, November 7, 2008

Spanos Auditorium

Download Video
Watch Quicktime Large
Watch Quicktime Small
Download Audio
Listen MP3


Biomagnetism is the phenomenon where magnetic fields are produced by the living things, especially by the human body; (different from magnetic fields applied to the body, called magnetobiology). The body's magnetic fields are very weak, and are measured with the sensitive detector called a SQUID (superconducting quantum interference device), usually in a magnetically shielded room, which excludes most external disturbances. There are about 160 laboratories around the world where fields from various parts of the body are measured; most measure the magnetic field from the brain, called the magnetoencephalogram, or MEG. The MEG shows complementary information to the electroencephalogram (EEG), and is producing valuable new information about the normal human brain. It also shows promise in clinical diagnosis of brain abnormalities. Thus, Biomagnetism is a promising new window into the human body generally, and into the brain, in particular. Thayer School of Engineering at Dartmouth is now acquiring a MEG system, and exciting developments are expected.

About the Speaker

David Cohen pioneered the study of Biomagnetism (magnetic fields produced by the body), where he made many of the first measurements. In 1969 Cohen built an elaborate shielded room at MIT, but still needed a more sensitive detector. James Zimmerman had just developed an extremely sensitive detector called the SQUID (Superconducting Quantum Interference Device). Cohen and Zimmerman set up this detector in the new room to look at the body's heart signal - the magnetocardiogram (MCG). For the first time the signals were clear, and their resulting report, called the magna carta of biomagnetism, ushered in a new era in biomagnetism. Cohen then measured the first clear signal from the brain or magnetoencephalogram (MEG). Cohen continuously worked in biomagnetism throughout his career, authored many publications, mostly concerning the MEG, and has been called "the father of the MEG". He remains active, is on the faculty at the Harvard Medical School, and is a mentor in the MEG group at the Martinos Center for Biomedical Imaging, which is located at Massachusetts General Hospital.