Although the reduction of Olig1-positive oligodendrocytes in CA4 did not reach significance, the trend towards significant reduction is in the same direction as in our stereological study and partly supports the notion of reduced oligodendrocyte numbers in the posterior part of the hippocampus in schizophrenia (Schmitt et al., 2009; Falkai et al., 2016). This evidence concerns the gene OLIG1 and schizophrenia.