Background. The histological basis of schizophrenia is
unknown,
but it appears to affect the hippocampal and neocortical cytoarchitecture.
Some
cytoarchitectural parameters normally differ
between the two cerebral hemispheres. Moreover, schizophrenia is associated
with
altered structural 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
density in sections from
the left and right hippocampus (dentate gyrus, CA4, CA3, CA1 and subiculum)
of
22 schizophrenics and 18 normal subjects. We also determined the correlations
of
neuronal density
between pairs 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 schizophrenics
compared
to the controls. (1) neuronal
density was increased 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) intra-hippocampal correlations 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 findings is consistent with a neurodevelopmental origin,
and with
a disease process
that affects cerebral asymmetry and leaves its imprint upon the hippocampal
cytoarchitecture.