Altered NRG1/ErbB4 signaling has been shown to contribute to NMDAR hypofunction in patients with schizophrenia (27) and mice with NRG1 deletion have 16% fewer functional NMDAR than wild-type mice, whereas if a similar change occurs also in ErbB4 KO mice was not determined (26). This evidence concerns the gene ERBB4 and schizophrenia.