Deficit of perineuronal oligodendrocytes in the inferior parietal lobule is associated with lack of insight in schizophrenia

Background and Objectives: Previously we reported a significant reduction in the numerical density of oligodendrocytes and oligodendrocyte clusters in the inferior parietal lobule (IPL) in schizophrenia that was associated with lack of insight. We also found a significant decrease in the number of perineuronal oligodendrocytes (PnOl) in the prefrontal cortex in schizophrenia and therefore we hypothesized that there may also be a deficit of PnOl in the IPL in schizophrenia and that it could be associated with poor insight. Methods: We estimated the number of PnOl adjacent to pyramidal neurons in layer 3 of BA39 and BA40 in Nissl stained sections from 24 males with schizophrenia and 24 normal male controls from the Stanley Parietal Collection. The schizophrenia group was divided into three subgroups based on level of insight: poor, fair or good. Results: We found a significant deficit of PnOl in layer 3 of BA39 and BA40 in the schizophrenia group as compared to the control group (p<0.01). In the control group but not in the schizophrenia group in BA39 the number of PnOl was significantly higher in the left hemisphere compared to the right hemisphere. In schizophrenia, in BA39 the number of PnOl was decreased in the subgroup with poor insight vs. controls. In BA40 the subgroups with both poor and fair insight were decreased vs. controls (p<0.01). In BA40 the subjects with fair insight also differed from those with good insight (p<0.01). Conclusions: The reduction of PnOl in the IPL in schizophrenia is associated with impaired insight and lack of hemispheric asymmetry.