Late auditory magnetic sources may differ in the left hemisphere of schizophrenic patients. A preliminary report

We recorded magnetoencephalographic auditory evoked fields from the left and right hemispheres of six medicated, paranoid schizophrenic subjects and six normal controls. The magnetic field data were used in estimating the location, orientation, and depth of the source generating the 100-millisecond latency evoked field component (M100). The M100 latencies were slightly shorter than simultaneously recorded vertex electroencephalographic evoked potential N100 latencies, suggesting that magnetoencephalographic and electroencephalographic recordings were examining slightly different aspects of the source(s). The M100 sources demonstrated substantial interhemispheric asymmetry in normal controls, and were located more posteriorly, with more nearly vertical orientations, over the left hemisphere. The M100 sources in schizophrenics did not exhibit the same interhemispheric asymmetry. Left hemisphere source orientation differed significantly between normal controls and schizophrenics. Discriminant function analysis correctly classified normal controls and schizophrenics at 100% using the conservative jackknife procedure on the basis of left hemisphere orientation alone. Our findings, while preliminary, support altered left hemisphere function, or possibly structure, in this group of schizophrenic subjects, and suggest that magnetoencephalographic recordings may be a useful research method in this major mental illness.