Effects of Brain Stimulation on Higher-Order Cognition

NCT ID: NCT03814967

Last Updated: 2025-07-29

Study Results

Results pending

The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.

Basic Information

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Recruitment Status

COMPLETED

Clinical Phase

NA

Total Enrollment

86 participants

Study Classification

INTERVENTIONAL

Study Start Date

2019-05-22

Study Completion Date

2025-05-31

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.

Detailed Description

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Conditions

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Schizophrenia

Study Design

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Allocation Method

RANDOMIZED

Intervention Model

CROSSOVER

Primary Study Purpose

BASIC_SCIENCE

Blinding Strategy

DOUBLE

Participants Investigators

Study Groups

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DLPFC Stimulation

Intervention. 20 minutes of 2 mA direct current stimulation over the dorsolateral prefrontal cortex.

Group Type EXPERIMENTAL

Transcranial Direct Current Stimulation

Intervention Type 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.

Occipital Stimulation

Intervention. 20 minutes of 2 mA direct current stimulation over the occipital cortex.

Group Type ACTIVE_COMPARATOR

Transcranial Direct Current Stimulation

Intervention Type 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.

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

Group Type SHAM_COMPARATOR

Transcranial Direct Current Stimulation

Intervention Type 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.

Interventions

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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.

Intervention Type DEVICE

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.


* 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
Minimum Eligible Age

18 Years

Maximum Eligible Age

50 Years

Eligible Sex

ALL

Accepts Healthy Volunteers

Yes

Sponsors

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University of California, Davis

OTHER

Sponsor Role lead

Responsible Party

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Responsibility Role SPONSOR

Locations

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Imaging Research Center

Sacramento, California, United States

Site Status

Countries

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United States

Related Links

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Other Identifiers

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UCD#3565

Identifier Type: OTHER

Identifier Source: secondary_id

1344169

Identifier Type: -

Identifier Source: org_study_id

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