David Cohen in 1969 with the not-yet-completed magnetically shielded room at MIT.
Last week the MGH Martinos Center dedicated its advanced magnetoencephalography (MEG) facility as the David Cohen MEG Laboratory. Cohen—the inventor of MEG, a leader in the field of biomagnetism for more than 50 years, and a Martinos Center faculty member who was instrumental in building and developing the facility in question—was on hand to help launch the rechristened lab.
In anticipation of the event, we delved into Cohen’s long, storied life and career, from his early days devising ways to measure the very weak magnetic fields originating in the human body to some of his equally impressive 21st-century accomplishments. Here are five things we learned.
1. In another life, Cohen was actually a “really strong magnetic field” kind of guy
Originally hailing from Canada, Cohen earned a PhD in Experimental Nuclear Physics from University of California, Berkley, in 1955. After a few one-year stints at other institutions, he joined the Argonne National Laboratory in Illinois, where he worked as an accelerator physicist specializing in strong magnetic fields and using heavy nuclear shielding. But his thoughts kept drifting to another topic, one on the opposite end of the spectrum. “I have a fancy job doing high-energy physics and working with big magnets,” he says, looking back on those early days. “And for some reason I’m thinking, year in and year out, wouldn’t it be fun to measure very weak magnetic fields”—that is, the kind of fields generated by the human body.
In 1963 a group in Syracuse reported the first measurement of the magnetic field of the human heart, using a pair of identical coils as a detector. Here, though, in order to minimize the magnetic disturbances associated with everyday urban life, they performed the experiments in the middle of a field, far away from the hustle and bustle of the city. Cohen had another idea: Instead of escaping background noise, simply minimize it by building a magnetically shielded room. He wrote a series of proposals to begin to explore the idea but he couldn’t get the higher-ups at Argonne on board. He would have to make his shielded room elsewhere.
2. Even the dullest of carpools can help to make history
You never know which connections will turn out to be life-changing ones. Every day during the years of 1957-1965, Cohen carpooled from the south side of Chicago to the Argonne facility, about an hour’s drive away. The ride was tedious at best—the same stale jokes, the same tired observations about the landscape passing by on the other side of the window—but it did give him the opportunity to develop a friendship with one of the other scientists: Lester Winsberg. “Lester was in my carpool, and we got to know each other quite well,” he says. “Well, somehow he got the idea that I was super brilliant; I assure you it was all a mistake.”
In 1964, Winsberg was appointed head of the physics department at the new University of Illinois campus in Chicago and tasked with hiring the faculty for the department. He knew Cohen was looking for a career change, hoping to pursue his idea of measuring biomagnetism using a shielded room. So he offered him a job as an associate professor of physics with the promise of tenure. And just as important: He would give him the money to build his “funny shielded room.”
It would be a risky move, leaving a fancy job at a big national laboratory for a relatively uncertain future at a state university, but Cohen knew he couldn’t pass up the opportunity. So he packed his bags and waved goodbye to his decade-plus career as an accelerator physicist.
3. A splashy article in the New York Times saved biomagnetism from the soul-crushing vagaries of academic politics
It’s tempting to believe that significant scientific breakthroughs were always meant to be, that the march of progress led inevitably to this one outcome, a discovery that had simply been waiting to be plucked from the ether. In many ways, though, the history of science is a history of near misses.
In 1967, two years after joining the faculty of the University of Illinois, Cohen published a paper in the journal Science—“Magnetic Fields around the Torso: Production by Electrical Activity of the Human Heart”—reporting the first measurements of biomagnetism using a shielded room to block out any unwanted magnetic noise. It was an important paper, and big news. The New York Times highlighted it—noting especially its potential to diagnose disease—other outlets picked it up, and the letters and phone calls started pouring in.
Unfortunately, the recognition did little to help an unhappy job situation at Illinois. Winsburg had recently been pushed out of his leadership position in the department and the new head wanted nothing to do with biomagnetism. Despite the promises made when he was hired, Cohen was not granted tenure. His career future, which not long before was looking so bright, was now as unclear as ever.
There was good news on the horizon, though. Ben Lax, the head of the prestigious Francis Bitter National Magnet Laboratory at MIT, knew all the buzz about the Science paper and was broadly intrigued by the work Cohen was doing. So when he learned Cohen had been denied tenure at Illinois he offered him a job: an Established Investigatorship of the American Heart Association, with the resources to set up a biomagnetism program at MIT. Five years, full salary, and no questions asked. It was, Cohen says, a dream come true.
4. MEG launched on New Year’s Eve 1969 with a prominent researcher stripped down to his shorts
What better way to celebrate the holiday, right?
By late 1969, Cohen had built a large, shielded room at the Francis Bitter lab at MIT—a pod-like structure with a stairway descending from an open panel on the side, it looked like something out of a science fiction movie—and was using it to measure the weak magnetic fields emanating from the human body. But the copper coil-based detector he had developed wasn’t yielding enough signal. To address this problem, he reached out to James Zimmerman, who had helped to introduce the superconducting quantum interference device (SQUID) some five years before when he was a researcher working with the Ford Motor Co. The SQUID could measure extremely weak magnetic fields but had not been used in humans.
“Jim arrived near the end of December, complete with SQUID, electronics, and nitrogen-shielded glass dewar,” he says. “It took a few days to set up his system in the 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 Cohen had seen with the copper coil-based detector. The implications of this were far reaching, and the reverberations from the experiment are still felt today. “Although I didn’t realize it, a new era had arrived in biomagnetism,” he says.
5. Cohen has been recognized by Guinness World Records. Twice.
Cohen led the Biomagnetism Group at MIT’s Francis Bitter Magnet Lab from 1969 to 1993, during which time he played an integral role in developing both the field of biomagnetism and the MEG technique, based on his seminal work from so many years ago. And though he “retired” in 1993 he has remained a highly productive investigator over the past quarter century: as a visiting scientist at MIT and, since 2001, an associate professor of radiology at Harvard Medical School and, of course, the MGH Martinos Center for Biomedical Imaging.
Today Cohen can look back on a lifetime of accomplishments. Many of these are now inscribed in the dusty, leather-bound tomes of the history of science. But there’s one that has largely escaped the attention of the academic community.
In a May 2013 issue of the journal Review of Scientific Instruments, Cohen and Sheraz Khan, an instructor in the Center who has worked closely with Cohen in recent years, reported the magnetic field of the wall of the shielded room in the Center’s MEG facility: an almost unimaginable 0.5 femtotesla/√Hz. (In recording biomagnetism, researchers want to account for any other sources of magnetism that might impact the measurement.) The paper caught the attention of the popular reference book and website Guinness World Records, which certified the finding as the ‘weakest magnetic field measured’—a record that still stands today.
This wasn’t the first time Cohen had made the pages of Guinness World Records. In the 1980s the book recognized him for what was then the weakest magnetic field ever measured: a field of 8 x 10-15 teslas, measured in the shielded room at the Francis Bitter lab at MIT. It was quite the accomplishment, recording such a weak signal. But of course in 2013, as so many times over the six decades plus of his research career, David Cohen outdid himself.