Middle and long latency peak sources in auditory evoked magnetic fields for tone bursts in humans.

The relative position of the P50m and the N100m sources of the auditory evoked magnetic field remains unclear. Magnetoencephalography was performed in 24 normal subjects. Contralateral P50m to left and right ear stimulus was observed in 21 and 19hemispheres, respectively. Ipsilateral P50m to left and right ear stimulus was observed in 17 and 16hemispheres, respectively. N100m was observed in all subjects for all stimuli. Relative position of the equivalent current dipole of the P50m was 1.0+/-7.6 (mean+/-SD) mm posterior, 2.0+/-5.8mm inferior and 1.8+/-8.0mm medial to the N100m dipole position considering all observations. We suggest that the P50m and N100m sources are colocated in an extended area of the cortex.