Effects of Brain Stimulation on Higher-Order Cognition

July 24, 2025 updated by: University of California, Davis

Transcranial Direct Current Stimulation (tDCS) Studies of Behavioral and Electrophysiological (EEG) Correlates of 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.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Actual)

86

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • United States
    • California
      • Sacramento, California, United States, 95817
        • Imaging Research Center

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years to 35 years (Adult)

Accepts Healthy Volunteers

Yes

Description

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

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

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

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: DLPFC Stimulation
Intervention. 20 minutes of 2 mA direct current stimulation over the dorsolateral prefrontal cortex.
Device: Transcranial 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.
Sham Comparator: Sham Stimulation
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
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.
Active Comparator: Occipital Stimulation
Intervention. 20 minutes of 2 mA direct current stimulation over the occipital cortex.
Device: Transcranial 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
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.
Assessment will begin immediately following stimulation and last for about 1.5 hours.
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).
Assessment will begin immediately following stimulation and last for about 1.5 hours.
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).
Assessment will begin immediately following stimulation and last for about 1.5 hours.

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of California, Davis

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

May 22, 2019

Primary Completion (Actual)

May 31, 2025

Study Completion (Actual)

May 31, 2025

Study Registration Dates

First Submitted

January 15, 2019

First Submitted That Met QC Criteria

January 18, 2019

First Posted (Actual)

January 24, 2019

Study Record Updates

Last Update Posted (Actual)

July 29, 2025

Last Update Submitted That Met QC Criteria

July 24, 2025

Last Verified

July 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 1344169
  • UCD#3565 (Other Identifier: University of CA Davis Psychiatry)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

Select data from this study may be submitted to the National Institute of Mental Health Data Archive (NDA). NDA is a data repository run by the National Institute of Mental Health (NIMH) that allows researchers studying mental illness to collect and share de-identified information with each other. The data repository is accessible only to qualified investigators. All subject data will be de-identified (subject names will not be used) and each subject will have a separate identifier called a Global Unique Identifier (GUID) to remove any possibility that "the identities of the subjects cannot be readily ascertained or otherwise associated with the data by the repository staff or secondary data users." (45 CFR, 46.102).

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

Yes

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

Clinical Trials on Schizophrenia

Clinical Trials on Transcranial Direct Current Stimulation

Search Similar Trials

Sponsors and Collaborators

Medical Conditions

Drug Interventions

CROs by country

CROs in Djibouti

Conditions

Rare Diseases

Drug Interventions

Dietary Supplements

Sponsor/Collaborators

Locations

Subscribe