Targeting Auditory Hallucinations With Alternating Current Stimulation

The investigator's primary objective is to provide further evidence for the effectiveness of transcranial alternating current stimulation (tACS) to treat auditory hallucinations and to collect preliminary data on whether maintenance stimulation sessions can prolong the duration of stimulation-induced clinical benefits. The investigators will be looking into effects of tACS to re-normalize pathological alpha oscillations in the dorso-lateral prefrontal cortex (dl-PFC) of patients with schizophrenia or schizo-affective disorder by comparing Auditory Hallucination Rating Scale (AHRS) scores immediately before the first stimulation session, immediately after the last stimulation session, and at the end of the 8 weeks of maintenance sessions. As a secondary objective, the investigators will assess the differential clinical effects of active sham and 10Hz tACS on electroencephalogram (EEG) measures of alpha oscillations. The investigators will also be using source localization techniques in EEG analysis, based on individual locations of the scalp electrodes and anatomical structures with the use of structural magnetic resonance imaging (sMRI).

Inclusion criteria

• DSM-IV diagnosis of schizophrenia, any subtype, or schizoaffective disorder with refractory hallucinations. Duration of illness >1 year
• 18 - 70 years old
• Clinical stable for at least 12 weeks i.e. not requiring any hospitalization or a change in level of care
• On current antipsychotic doses for at least 4 weeks
• Experience at least 3 auditory hallucinations per week
• Stable auditory hallucinations as demonstrated by having less than or equal to 20% change in AHRS scores across a 2 week interval during the screening period
• Capacity to understand all relevant risks and potential benefits of the study and to provide written informed consent, OR has a legal guardian who can provide the informed consent on the patient's behalf with the patient providing written assent to participate

Exclusion criteria

• DSM-IV diagnosis of alcohol or substance abuse (other than nicotine) within the last month or a DSM-IV diagnosis of alcohol or substance dependence (other than nicotine) within the last 6 months
• Positive urine test of cannabis, cocaine, amphetamine, barbiturates, opiates
• Current treatment (within 4 weeks) with psychotropic agents including benzodiazepines that are taken on a daily basis (limit prn use to greater than 48 hours before participating in a study session)
• Medical or neurological illness (unstable cardiac disease, AIDS, malignancy, liver or renal impairment) or treatment for a medical disorder that could interfere with study participation
• history of traumatic brain injury that required subsequent cognitive rehabilitation, or caused cognitive sequelae
• A difference of greater than 20% in AHRS scores between screening visits
• Prior brain surgery
• Any brain devices/implants, including cochlear implants and aneurysm clips
• Co-morbid neurological condition (e.g. seizure disorder, brain tumor)
• Non English speakers
• Female participants who are pregnant, nursing, or unwilling to use appropriate birth control measures during study participation
• Anything that, in the opinion of the investigator, would place the participant at increased risk or preclude the participants' full compliance with or completion of the study