Schizophrenia is a serious disorder which affects how a person thinks, feels and acts. Someone with schizophrenia may have difficulty distinguishing between what is real and what is imaginary; may be unresponsive or withdrawn; and may have difficulty expressing normal emotions in social situations. Schizophrenia is characterized by core impairments including positive symptoms (hallucinations, delusions), negative symptoms (blunted affect, alogia, social deficits, anhedonia, avolition), as well as persistent neurocognitive deficits (memory, concentration, and learning). Positive symptoms usually show good response to currently approved medications, all of which act exclusively by blocking D2 receptors. Alternatively, the negative and neurocognitive symptoms respond poorly to D2 antagonists, and therefore persist even in treated patients.