Anomalies of asymmetry of pyramidal cell density and structure in dorsolateral prefrontal cortex in schizophrenia

Background Studies suggest that neuronal density in left dorsolateral prefrontal cortex is increased in schizophrenia. Aims To replicate these findings and extend them to both hemispheres. Method Neuronal density, size and shape were estimated in the prefrontal cortex (Brodmann area 9) of the left and right hemispheres of brains taken postmortem from 10 people with schizophrenia and 10 without mental illness (6 men, 4 women in both groups). Results Overall neuronal density (individually corrected for shrinkage) did not differ between the groups. In the control brains, density was generally greater in the left than the right hemisphere, the reverse was seen in the schizophrenia brains; this loss or reversal of asymmetry was most significant in cortical layer 3. Pyramidal neurons in this cell layer were significantly larger on the left and more spherical in shape than on the right side in control brains, but size and shape did not differ between the two sides in schizophrenia. Non-pyramidal and glial cell densities were unchanged. Conclusions We failed to find an increase in neuronal density, but found evidence at a cellular level of loss or reversal of asymmetry, consistent with the hypothesis of a primary change in the relative development of areas of heteromodal association cortex in the two hemispheres.