SQUID TECHNOLOGY AND BRAIN RESEARCH

Since 1968, SQUIDs have been used in many low temperature laboratories as ultrasensitive detectors of magnetic flux. Multi-SQUID application s, however, have materialized only recently. Neuromagnetometers are no w available covering the whole head in a helmet-like fashion with over 100 superconducting sensors. These instruments are used in magnetoenc ephalography (MEG) for recording the very weak fields, on the order of 100 fT, which are produced by electrical currents flowing in the brai n's neural networks. From the externally measured magnetic field distr ibution it is possible to calculate the active sites in the cortex. Th e spatial resolution of MEG is, under favorable conditions, 4-5 mm and the temporal accuracy is better than 1 ms. The method can thus be emp loyed for noninvasive studies of basic neurophysiological functions an d information processing in the human brain. Clinical applications are emerging as well. Two examples of recent work using our 122-SQUID mag netometer are discussed.