In autopsy samples, it was found that the expression of t-DARPP-32 increased in the prefrontal cortex of patients with schizophrenia and bipolar disorder, and the genotype with high expression of full-length DARPP-32 and low expression of truncated DARPP-32 has large volume of the prefrontal cortex. The gene discussed is PPP1R1B; the disease is bipolar disorder.