Effects of PFC tDCS on Cognitive Control, Attention Lapses and Coordinated Neural Activity in the Theta and Alpha Bands

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. Our 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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Effects of PFC tDCS on Cognitive Control, Attention Lapses and Coordinated Neural Activity in the Theta and Alpha Bands

Conditions
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Healthy

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: between ages of 18 and 50 ability to sufficiently speak and understand English so as to be able to understand and complete cognitive tasks ability to give valid informed consent Exclusion Criteria: no history of head trauma no current or previous history of treatment with psychotropic medication corrected vision 20/30 or better tDCS/MRI contraindications, including: pregnancy, ferrous metal in any part of the body, serious medical conditions, claustrophobia, metallic implants, skin damage, conditions such as eczema at electrode sites, cranial pathologies

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. The targeted brain area is determined by the Study Arm.<br>|
| Experimental: 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. The targeted brain area is determined by the Study Arm.<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. The targeted brain area is determined by the Study Arm.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Behavioral Cognitive Control Measures on the Stroop Task | Incongruent versus Congruent difference in error rate and reaction time | Through study completion, an average of 1 month | 
| EEG Cognitive Control Measures on the Stroop Task | response-locked power in the theta frequency band (4-7 Hz) | Through study completion, an average of 1 month | 
| Behavioral Attention Lapse Measures on the Stroop Task | Error Rate on Incorrect Congruent trials (Full Lapses) and Slow-but-Correct Congruent trials (Partial Lapses) | Through study completion, an average of 1 month | 
| EEG Attention Lapse Measures on the Stroop Task EEG Attention Lapse Measures on the Stroop Task | Pre-trial power in the alpha frequency band (8-12 Hz) | Through study completion, an average of 1 month | 
| Behavioral Cognitive Control Measures on the Change Detection Task Behavioral Cognitive Control Measures on the Change Detection Task | WM storage capacity (k-max) | Through study completion, an average of 1 month | 
| EEG Cognitive Control Measures on the Change Detection Task | delay period power in the theta frequency band (4-7 Hz) | Through study completion, an average of 1 month | 
| Behavioral Attention Lapse Measures on the Change Detection Task | Attention factor (a); Guess factor (g) | Through study completion, an average of 1 month | 
| EEG Attention Lapse Measures on the Change Detection Task | Pre-trial power in the alpha frequency band (8-12 Hz) | Through study completion, an average of 1 month | 
| Delivered tDCS Dose to PFC | Estimated electric field in PFC region of interest | Through study completion, an average of 1 month |