Intermediate Physics for Medicine and Biology: David Cohen: The Father of MEG

Friday, July 11, 2025

David Cohen: The Father of MEG

David Cohen: The
Father of MEG,
by Gary Boas.

Gary Boas recently published a short biography of David Cohen, known as the father of magnetoencephalography (MEG). The book begins with Cohen’s childhood in Winnipeg, Canada, including the influence of his uncle who introduced him to electronics and crystal radios. It then describes his college days and his graduate studies at the University of California, Berkeley. He was a professor at the University of Illinois Chicago, where he built his first magnetically shielded room in which he hoped to measure the magnetic fields of the body. Unfortunately, Cohen didn’t get tenure there, mainly for political reasons (and a bias against applied research related to biology and medicine). However, he found a new professorship at the Massachusetts Institute of Technology, where he built an even bigger shielded room. The climax of several years of work came in 1969, when he combined the SQUID magnetometer and his shielded room to make groundbreaking biomagnetic recordings. Boas describes the big event this way:

To address this problem [of noise in his copper-coil based magnetic field detector drowning out the signal], he [David Cohen] turned to James Zimmerman, who had invented a superconducting quantum interference device (SQUID) several years before… The introduction came by way of Ed Edelsack, a U.S. Navy funding officer… In a 2024 retrospective about his biomagnetism work in Boston, David described what happened next.

“Ed put me in touch with Jim, and it was arranged that Jim would bring one of his first SQUIDs to my lab at MIT, to look for biomagnetic signals in the shielded room. Jim arrived near the end of December, complete with SQUID, electronics, and nitrogen-shielded glass dewar. It took a few days to set up his system in the shielded room, and for Jim to tune the SQUID. Finally, we were ready to look at the easiest biomagnetic signal: the signal from the human heart, because it was large and regular. Jim stripped down to his shorts, and it was his heart that we first looked at.”

The results were nothing short of astounding; in terms of the signal measured, they were light years beyond anything David had seen with the copper-coil based detector. By combining the highly sensitive SQUID with the shielded room, which successfully eliminated outside magnetic disturbances, the two researchers were able to produce, for the first time, clear, unambiguous signals showing the magnetic fields produced by various organs of the human body. The implications of this were far reaching, with potential for a wide range of both basic science and clinical applications. David didn’t quite realize this at the time, but he and Zimmerman had just launched a new field of study, biomagnetism…

Having demonstrated the efficacy of the new approach… David switched off the lights in the lab and he and Zimmerman went out to celebrate. It was December 31, 1969. The thrill of possibility hung in the air as they joined other revelers to ring in a new decade—indeed, a new era.

“Biomagnetism: The
First Sixty Years.”

The biography is an interesting read. I always enjoy stories illustrating how physicists become interested in biology and medicine. Russ Hobbie and I discuss the MEG in Chapter 8 of Intermediate Physics for Medicine and Biology.You can also learn more about Cohen's contributions in my review article “Biomagnetism: The First Sixty Years.”

Today Cohen is 97 years old and still active in the field of biomagnetism. The best thing about Boas’s biography is you can read it for free at https://meg.martinos.org/david-cohen-the-father-of-meg. Enjoy!