Interestingly, a recent postmortem study comparing the levels of KP metabolites in the brains of patients with schizophrenia and healthy controls found increased QUIN and KYNA levels in the WM but not in the gray matter of the prefrontal cortex [94], corroborating previous findings of WM abnormalities associated with KP activation [95]. This evidence concerns the gene NPPA and schizophrenia.