A new method for magnetoencephalography: A three-dimensional magnetometer spatial filter system

A novel three-dimensional magnetometer-spatial filter system was developed to study human brain activity with high spatiotemporal resolution. The syst em combines the high temporal resolution of magnetoencephalography with the high spatial resolution achieved by using three-dimensional magnetometers and spatial filters to measure the direction and intensity of magnetic fiel ds generated during brain activity. Simulation and phantom studies indicate that the system is capable of mapping current sources of magnetic fields w ith a spatial resolution comparable to that of any other brain functional i maging technique while maintaining millisecond temporal resolution. Applica tion of this system to the human brain resolved magnetoencephalographic res ponses evoked by motion stimuli on a millisecond scale into responses occur ring in visual cortical areas V1, V2/3 and V5. It also revealed signals rel ated to contextual modulation in V1 and V2/3. This system provides a new way of studying the dynamics of human brain func tion. (C) 1999 IBRO. Published by Elsevier Science Ltd.