David Cohen made many of the first pioneering measurements in the area of biomagnetism (magnetic fields produced by the body), although he was initially trained as a nuclear physicist.

Early life and education

Cohen was born of immigrant parents in

Winnipeg Winnipeg () is the capital and largest city of the province of Manitoba in Canada. It is centred on the confluence of the Red and Assiniboine rivers, near the longitudinal centre of North America. , Winnipeg had a city population of 749,6 ...

, Manitoba, Canada. He was raised there and earned a B.A. degree at the

University of Manitoba The University of Manitoba (U of M, UManitoba, or UM) is a Canadian public research university in the province of Manitoba.University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant u ...

, where he gained a Ph.D. in experimental nuclear physics.

Career

Working in this area, and using large magnets, he became interested in the other extreme; this was the measurement of very weak magnetic fields, which for example might be produced by the weak natural currents in the human body. In 1963, he proposed a method using a magnetically shielded room to keep out external magnetic disturbances, as in radiation shielding in nuclear experiments. At that time others reported the first biomagnetic measurement, where the MCG (''magnetocardiogram'', the magnetic field due to heart currents) was measured; this was done without shielding, hence showed much external interference. Cohen then built a modest shielded room, and with somewhat clearer signals verified the heart's magnetic field. He also made the first measurement of the MEG (''

magnetoencephalogram Magnetoencephalography (MEG) is a functional neuroimaging technique for mapping brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain, using very sensitive magnetometers. Arrays of SQUIDs ...

'', the magnetic field of the brain). However, all these early biomagnetic measurements were generally too noisy, both because of the use of insensitive detectors, and incomplete magnetic shielding. To obtain clearer results, in 1969 Cohen built an elaborate shielded room at

MIT The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the m ...

, but still needed a more sensitive detector. James Zimmerman had just developed an extremely sensitive detector called the

SQUID True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting t ...

(''Superconducting Quantum Interference Device''). Cohen and Zimmerman set up this detector in the new room, to look at the body's heart signal, the MCG. For the first time the signals were now clear, and their resulting report, called the ''magna carta of biomagnetism'', ushered in a new era in biomagnetism, attracting other researchers. Cohen then measured the first clear MEG, and signals from other organs. As interest rapidly grew, other laboratories also produced new recordings. Today, most biomagnetic measurements are of the human brain (MEG); these are made in a shielded room, using a helmet over the head containing hundreds of

s. There are perhaps 200 such MEG systems in existence, worldwide. Cohen continuously worked in biomagnetism, authored many publications, mostly concerning the MEG, and has been called "the father of the MEG".''Science'' (Research News story by R. Crease), July 26, 1991; 374-5. He remains active in 2017, is on the faculty at the

Harvard Medical School Harvard Medical School (HMS) is the graduate medical school of Harvard University and is located in the Longwood Medical Area of Boston, Massachusetts. Founded in 1782, HMS is one of the oldest medical schools in the United States and is consi ...

, and is a mentor in the MEG group at MIT's Martinos Center, located at Massachusetts General Hospital.

Notes

External links

* http://davidcohen.mit.edu * https://web.archive.org/web/20071229153725/http://www.nmr.mgh.harvard.edu/martinos/people/showPerson.php?people_id=33 * http://www.Biomag2004.net {{DEFAULTSORT:Cohen, David Canadian biophysicists Canadian physicists Canadian nuclear physicists Experimental physicists Living people Harvard Medical School faculty UC Berkeley College of Letters and Science alumni Year of birth missing (living people)

Early life and education

Career

See also

Notes

External links