REVERSAL OF CEREBRAL ASYMMETRY IN SCHIZOPHRENIA MEASURED WITH MAGNETOENCEPHALOGRAPHY

It has been suggested that schizophrenic patients fail to develop left -hemisphere dominance because of an early disturbance in neuronal deve lopment. This hypothesis has been supported by some post-mortem. CT an d magnetic resonance imaging (MRI) studies. While other in-vivo studie s have given contradicting results. We used 122-channal whole-head mag netoencephalography and MRI to locate the sources of auditory evoked r esponses in 19 schizophrenic patients and in 20 healthy controls. Audi tory evoked responses were detected in all subjects. The left-right he misphere asymmetry of cerebral sources for auditory evoked responses w as markedly dispersed among patients when compared with controls. The source locations for left auditory cortex were clearly anterior with r espect to the right hemisphere in 32% of the patients. While the corre sponding prevalence of this abnormal asymmetry was 0% in controls (p=0 .008. Fisher's exact test). The reversed asymmetry appeared to be asso ciated with a shorter anterior-posterior distance between the auditory cortex and the anterior tip of the temporal lobe in the left side whe n compared with the right side. The reversed asymmetry was associated with higher PANSS general psychopathological score, and especially wit h higher guilt feelings and motor retardation scores. The large 2.5-fo ld standard deviation in the inter-hemispheric anterior-posterior diff erence in the location of the auditory cortex among patients (p=0.001 for the difference in the magnitude of variance between controls and p atients) clearly reflects the dispersion of the left-right asymmetry i nto both directions, and three of the patients with 'normal asymmetry' had a greater left-right asymmetry than any of the controls. Markedly greater reversal of hemispheric asymmetry among patients implies that regulation of the development of brain asymmetry is disturbed among s chizophrenic patients. Abnormality in the cerebral asymmetry may be a crucial factor in the development of schizophrenic disorder in a subst antial proportion of patients. The results suggest that the reversed a symmetry is associated with the higher severity of general psychopatho logical symptoms. (C) 1998 Elsevier Science B.V.