PVALB and schizophrenia: Parvalbumin interneurons are predominantly found in the middle and lower cortical layers (Hof et al. 1999; Tooney and Chahl 2004) and have been shown to be most affected in layers 3 and 4 in schizophrenia (Chung et al. 2016b; Hashimoto et al. 2003; Sakai et al. 2008; Tooney and Chahl 2004), and it maybe that averaging across layers underestimates the greater differences found between patients with schizophrenia and controls.