Cerebellar Modulation of Cognition in Psychosis

Inclusion Criteria: * Age between 18-55 years * Diagnosis of a psychotic disorder (i.e. schizophrenia or schizoaffective disorder or bipolar disorder type I) * Must be able to read, speak and understand English * Must be judged by study staff to be capable of completing the study procedures * Participants will be in stable outpatient treatment with no recent (within the past 30 days) hospitalizations or changes in their medication regimens. Exclusion Criteria: * Diagnostic and Statistical Manual 5 diagnosis of moderate substance use disorder within the past month * Conditions that might result in increased risks of side effects or complications from rTMS or MRI, including: * Intracranial pathology from a known genetic disorder (e.g., Neurofibromatosis 1, tuberous sclerosis) or from acquired neurologic disease (e.g. stroke, tumor), cerebral palsy, history of severe head injury, or significant dysmorphology; * History of fainting spells of unknown or undetermined etiology that might constitute seizures * History of multiple seizures or diagnosis of epilepsy * Any progressive (e.g., neurodegenerative) neurological disorder such as multiple sclerosis or Parkinson's disease * Chronic (particularly) uncontrolled medical conditions that may cause a medical emergency in case of a provoked seizure (cardiac malformation, cardiac dysrhythmia, asthma, etc.) * Metal implants (excluding dental fillings) unless cleared by the responsible covering MD (i.e. MRI compatible joint replacement) * Pacemaker * Implanted medication pump * Vagal nerve stimulator * Deep brain stimulator or transcutaneous electric nerve stimulation unit * Ventriculo-peritoneal shunt * Signs of increased intracranial pressure * Intracranial lesion * History of head injury resulting in prolonged loss of consciousness (\>15minutes) or neurological sequelae * Pregnancy: All participants capable of becoming pregnant will be required to have a pregnancy test; any participant who is pregnant will not be enrolled in the study.