Effects of Brain Stimulation on Higher-Order Cognition

Study Overview
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Brief Summary
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The purpose of this study is to better understand the neural correlates of higher-order cognition, both in the healthy brain and in schizophrenia, and to determine how these mechanisms are modulated by transcranial direct current stimulation (tDCS) at frontal and occipital scalp sites. Testing the effects of tDCS at these scalp sites on cognitive task performance will help us understand the roles of the brain regions corresponding to these sites during higher-order cognitive processing (language comprehension, cognitive control, and related attention and memory processes). Behavioral and electrophysiological (EEG) measures will be used to assess cognitive performance. The investigator's overarching hypothesis is that stimulating prefrontal circuits with tDCS can improve cognitive control performance, and ultimately performance on a range of cognitive tasks, as compared to stimulating a different cortical region (occipital cortex) or using sham stimulation. This study is solely intended as basic research in order to understand brain function in healthy individuals and individuals with schizophrenia. This study is not intended to diagnose, cure or treat schizophrenia or any other disease.

Official Title
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Transcranial Direct Current Stimulation (tDCS) Studies of Behavioral and Electrophysiological (EEG) Correlates of Higher-Order Cognition

Conditions
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Schizophrenia

Intervention / Treatment
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* Device: Transcranial Direct Current Stimulation


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Participants must be able to sufficiently speak and understand English so as to be able to understand and complete cognitive tasks. All subjects must have the ability to give valid informed consent. Inclusion Criteria for Patients with Schizophrenia Only: Diagnosis of schizophrenia, schizophreniform or schizoaffective disorder No medication changes in the prior month No medication changes anticipated in the upcoming month Stable outpatient or partial hospital status Normal IQ (>70; IQ will be measured by administering the Wechsler Abbreviated Scale of Intelligence (WASI) test) Exclusion Criteria: Pacemakers Implanted electrical (brain and spinal) stimulators Implanted defibrillator Metallic implants Skin damage or skin conditions such as eczema at the sites where electrodes will be placed Hair styles hindering the placement of electrodes Cranial pathologies Head trauma Epilepsy Mental retardation Any known history of neurological disorders (including epilepsy, amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), stroke, cerebral palsy, any DSM-5 axis I psychiatric disorder (for healthy control subjects), autism) Uncorrected vision problems that would hinder cognitive testing (this also pertains to subjects with color blindness in tasks where discriminating colored objects/items is necessary for successful performance) Pregnancy Substance dependence in the past six months Substance abuse in the past month

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 50 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: DLPFC Stimulation<br>Intervention. 20 minutes of 2 mA direct current stimulation over the dorsolateral prefrontal cortex. | Device: Transcranial Direct Current Stimulation<br>* In tDCS, saline-soaked electrodes are temporary affixed to the scalp and connected to a battery-powered current generator. A weak (2 mA) constant current is then briefly applied ( 20 minutes) to stimulate the targeted brain area (e.g. the DLPFC). To control for placebo effects, the study will utilize a sham stimulation protocol that consists of very brief constant stimulation ( 1 minute). Subjects usually cannot discern the difference between the sham and experimental stimulation protocols due to habituation.<br>|
| Active Comparator: Occipital Stimulation<br>Intervention. 20 minutes of 2 mA direct current stimulation over the occipital cortex. | Device: Transcranial Direct Current Stimulation<br>* In tDCS, saline-soaked electrodes are temporary affixed to the scalp and connected to a battery-powered current generator. A weak (2 mA) constant current is then briefly applied ( 20 minutes) to stimulate the targeted brain area (e.g. the DLPFC). To control for placebo effects, the study will utilize a sham stimulation protocol that consists of very brief constant stimulation ( 1 minute). Subjects usually cannot discern the difference between the sham and experimental stimulation protocols due to habituation.<br>|
| Sham Comparator: Sham Stimulation<br>Placebo Comparator. 0.5-1 minutes of 2 mA direct current stimulation over the dorsolateral prefrontal cortex followed by 19-19.5 minutes of sham stimulation | Device: Transcranial Direct Current Stimulation<br>* In tDCS, saline-soaked electrodes are temporary affixed to the scalp and connected to a battery-powered current generator. A weak (2 mA) constant current is then briefly applied ( 20 minutes) to stimulate the targeted brain area (e.g. the DLPFC). To control for placebo effects, the study will utilize a sham stimulation protocol that consists of very brief constant stimulation ( 1 minute). Subjects usually cannot discern the difference between the sham and experimental stimulation protocols due to habituation.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| EEG Correlates of Language and Cognitive Control | Electrophysiological data recorded during completion of cognitive control and language comprehension tasks. We will measure oscillatory activity in the theta, alpha, beta and gamma frequency bands. | Assessment will begin immediately following stimulation and last for about 1.5 hours. | 
| Behavioral Response (Cognitive Control Task) | We will assess performance on the Dot Pattern Expectancy (DPX) task (error rates and d-prime scores). | Assessment will begin immediately following stimulation and last for about 1.5 hours. | 
| Behavioral Response (Language Task) | We will assess performance on a novel Language Comprehension task (accuracy and semantic relatedness judgement scores). | Assessment will begin immediately following stimulation and last for about 1.5 hours. | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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schizophrenia, EEG, tDCS, dorsolateral prefrontal cortex, cognitive control, language, transcranial direct current stimulation