Measurement of slowly changing magnetic sources in the brain

Slowly changing magnetic sources in the brain, rising and falling with a time course of minutes, have been associated with major pathological disturbances of ion concentrations in Spreading Depression. The authors describe progress and issues that arise in the application to human subjects of a technique devised to improve the resolution of such very low frequency (0.001-0.1 Hz) MEG recordings. It would be of value to obtain improved records from patients with concussion, stroke, and migraine. Slow signals may also occur in normal subjects