A Study to Evaluate the Safety and Efficacy of BIIB104 in Participants With Cognitive Impairment Associated With Schizophrenia (CIAS)

Key Inclusion Criteria: * Otherwise healthy participant with a Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), diagnosis of schizophrenia of at least 2 years' duration as confirmed by the mini-international neuropsychiatric interview (MINI) 7.0.2 for Psychotic Disorders. * Evidence of stable schizophrenia symptomatology ≥12 weeks (e.g., no hospitalizations for schizophrenia, no increase in level of psychiatric care due to worsening of schizophrenia symptoms). * Participants must be in ongoing maintenance atypical antipsychotic therapy (except clozapine), on a stable treatment regimen for ≥8 weeks prior to Baseline/Day 1, including concomitant psychotropic medication. Doses of background atypical antipsychotics should be within the recommended dose range listed in the approved product labeling of the country where the study is being conducted. * SCI-PANSS: No more than moderate-severe rating (score ≤5) on delusions, hallucinatory behavior, grandiosity, suspiciousness / persecution, and hostility (i.e. PANSS, positive symptom items P1, P3, P5, P6, P7); or unusual thought content (G9); and no more than a moderate rating (score ≤4) on conceptual disorganization (P2). Key Exclusion Criteria: * Participation in a trial using any component or version of the MATRICS Consensus Cognitive Battery (MCCB) or the University of California, San Diego (UCSD) Performance-Based Skills Assessment test within the previous 6 months. * Participation in cognitive rem…