Loss of ErbB4 in PV+ interneurons also causes a non-cell autonomous reduction in the density of dendritic spines in pyramidal cells (Pino et al., 2013; Yin et al., 2013), suggesting that this characteristic pathological feature of schizophrenia might be – at least theoretically – a secondary adaptation to defective inhibition in the cerebral cortex. This evidence concerns the gene ERBB4 and schizophrenia.