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.