REPRODUCIBILITY OF MEG AUDITORY-EVOKED FIELD SOURCE LOCALIZATIONS IN NORMAL HUMAN-SUBJECTS USING A 7-CHANNEL GRADIOMETER

Magnetoencephalographic (MEG) auditory evoked fields (EF) were recorde d from 12 normal adult subjects over both hemispheres on two separate occasions at least one week apart using a seven-channel second-order g radiometer, Stimuli were computer-generated at 25-msec duration, 1 kHz tone pips, Responses to 100 stimuli were averaged, and source estimat es with confidence intervals were computed, for the 100-msec latency a uditory EF component, termed M100. Root-mean-squared (rms) differences in x, y, and z locations were approximately 0.7 cm on the two occasio ns; strength and orientation differences were 18 nA-m and 11 degrees, respectively. This spatial accuracy using a seven-channel instrument, compares favorably with other currently available technologies for loc alization of brain function.