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OpenTrials
Completed

NCT Number: NCT03814967

Effects of Brain Stimulation on Higher-Order Cognition

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.

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Key information

Conditions

Schizophrenia Behavior Communication Language Mental Disorders Schizophrenia Spectrum and Other Psychotic Disorders

Age range

18 year–50 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Imaging Research Center

Sacramento, California, 95817, United States

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

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

Treatment and study plan

Transcranial Direct Current Stimulation

Device

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.

Primary outcomes

  1. EEG Correlates of Language and Cognitive Control

    Time frame: 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.

  2. Behavioral Response (Cognitive Control Task)

    Time frame: 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).

  3. Behavioral Response (Language Task)

    Time frame: 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).

Sponsors and collaborators

Lead sponsor

University of California, Davis

Other

Registry information

Official study title

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

Important dates

Study start
2019
Primary completion
2025
Study completion
2025
First posted
Jan 24, 2019
Registry last updated
Jul 29, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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