THE HIPPOCAMPUS IN SCHIZOPHRENIA - LATERALIZED INCREASE IN NEURONAL DENSITY AND ALTERED CYTOARCHITECTURAL ASYMMETRY

Background. The histological basis of schizophrenia is unknown, but it appears to affect the hippocampal and neocortical cytoarchitecture. S ome cytoarchitectural parameters normally differ between the two cereb ral hemispheres. Moreover, schizophrenia is associated with altered st ructural cerebral asymmetry. However, few cytoarchitectural studies of schizophrenia have taken the question of asymmetry fully into account . Methods. We performed a morphometric post mortem study of neuronal d ensity in sections from the left and right hippocampus (dentate gyrus, CA4, CA3, CA1 and subiculum) of 22 schizophrenics and 18 normal subje cts. We also determined the correlations of neuronal density between p airs of subfields as an index of their inter-relationship; a previous study had found correlations in the left but not the right hippocampus of normal subjects. Results. There were three differences in the schi zophrenics compared to the controls. (1) neuronal density was increase d in right CA3 (by 25 %) and right CA1 (by 22 %); (2) neuronal density correlated strongly between homologous left and right subfields (i.e. inter-hippocampally) for CA4, CA3, CA1 and subiculum, in normals this occurs only for dentate gyrus and CA4; and (3) intrahippocampal corre lations of neuronal density between pairs of subfields were similar in both hippocampi of the schizophrenia cases, unlike their asymmetrical distribution in controls. Conclusions. The alterations may be part of the histological substrate of schizophrenia. The nature of the findin gs is consistent with a neurodevelopmental origin, and with a disease process that affects cerebral asymmetry and leaves its imprint upon th e hippocampal cytoarchitecture.