Schizophrenia
Conditions
Keywords
schizophrenia, EEG, tDCS, dorsolateral prefrontal cortex, cognitive control, language, transcranial direct current stimulation
Brief summary
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.
Interventions
DEVICETranscranial Direct Current Stimulation
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.
Sponsors
University of California, Davis
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
DOUBLE (Subject, Investigator)
Eligibility
Sex/Gender
ALL
Age
18 Years to 50 Years
Healthy volunteers
Yes
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| EEG Correlates of Language and Cognitive Control | Assessment will begin immediately following stimulation and last for about 1.5 hours. | 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. |
| Behavioral Response (Cognitive Control Task) | Assessment will begin immediately following stimulation and last for about 1.5 hours. | We will assess performance on the Dot Pattern Expectancy (DPX) task (error rates and d-prime scores). |
| Behavioral Response (Language Task) | Assessment will begin immediately following stimulation and last for about 1.5 hours. | We will assess performance on a novel Language Comprehension task (accuracy and semantic relatedness judgement scores). |
Countries
United States
Outcome results
None listed