David Cohen made many of the first pioneering measurements in the area of

biomagnetism Biomagnetism is the phenomenon of magnetic fields ''produced'' by living organisms; it is a subset of bioelectromagnetism. In contrast, organisms' use of magnetism in navigation is magnetoception and the study of the magnetic fields' ''effects'' ...

(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 Provinces and territories of Canada, Canadian province of Manitoba. It is centred on the confluence of the Red River of the North, Red and Assiniboine River, Assiniboine rivers. , Winnipeg h ...

, 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 public research university in Winnipeg, Manitoba, Canada. Founded in 1877, it is the first university of Western Canada. Both by total student enrolment and campus area, the University of ...

. Then, he attended graduate school at the

University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California), is a Public university, public Land-grant university, land-grant research university in Berkeley, California, United States. Founded in 1868 and named after t ...

, 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 (s ...

'', 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 research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of modern technology and sc ...

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

SQUID A squid (: squid) is a mollusc with an elongated soft body, large eyes, eight cephalopod limb, arms, and two tentacles in the orders Myopsida, Oegopsida, and Bathyteuthida (though many other molluscs within the broader Neocoleoidea are also ...

(''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 medical school of Harvard University and is located in the Longwood Medical and Academic Area, Longwood Medical Area in Boston, Massachusetts. Founded in 1782, HMS is the third oldest medical school in the Un ...

, 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