NEUROMAGNETIC LOCALIZATION USING MAGNETIC-RESONANCE IMAGES

Ionic flow associated with neural activation of the brain produces a m agnetic field, called the neuromagnetic field, that can be measured ou tside the head using a highly sensitive superconducting quantum interf erence device (SQUID) based neuromagnetometer. Under certain condition s, the sources producing the neuromagnetic field are localizable from a sampling of the neuromagnetic field. Neuromagnetic measurements alon e, however, do not contain sufficient information to visualize brain s tructure. Thus, it becomes necessary to combine neuromagnetic localiza tion with an anatomical imaging technique such as magnetic resonance i maging (MRI) to visualize both function and anatomy in vivo. Using exp erimentally measured human neuromagnetic fields and magnetic resonance images, we have developed a technique to register accurately these tw o modalities and have applied the registration procedure to portray th e spatiotemporal distribution of neural activity evoked by auditory st imulation.