Study to Evaluate the Safety and Efficacy of MEM 3454 as Adjunctive Treatment in Combination With a Preexisting Antipsychotic in Patients With Cognitive Impairment Associated With Schizophrenia

Inclusion Criteria: * Diagnosis of schizophrenia (any subtype), assessed using a structured interview. * At least one month on the same dose of antipsychotic medication. * Clinically stable, as judged by the investigator, and in a non-acute phase for at least 12 weeks. * Able to provide informed consent. * Fluent in English. * Smokers and non-smokers. Exclusion Criteria: * First 3 years of schizophrenia diagnosis. * Current risk of suicide, or history of suicidal behavior within the last 6 months. * Hospitalized for psychiatric symptoms in the past 3 months. * Other psychiatric diagnoses. * Substance abuse/dependence (other than nicotine or caffeine) within the last 6 months according. * Nicotine replacement therapy, smoking cessation medications or remedies, including Varenicline (Chantix).