Effects of Non-Invasive Brain Stimulation on Soldiers' Cognitive and Functional Performance

Non-invasive brain stimulation has been shown to alter performance in both clinical and healthy populations on cognitive tasks. While the performance alterations have generally been shown to result in enhancement, mixed results remain in the literature. Much of the mixed results within the literature have been attributed to the use of different stimulation parameters, targeting of different brain areas, and using a variety of performance measures or assessing different constructs. However, non-invasive brain stimulation is a desirable method for enhancing Soldier performance given the ease of administration and minimal side effects as compared to other forms of performance enhancement (e.g., pharmaceuticals, caffeine). The objective of the current study is to evaluate the effects of non-invasive brain stimulation to the left dorsolateral prefrontal cortex in enhancing Soldier cognitive skills and performance on military tasks. A double blind within-subjects design will be used with healthy, rested Soldiers who will receive non-invasive brain stimulation and perform basic cognitive and operationally relevant tasks.

Study Overview

• Status: Completed
• Conditions: Performance Enhancement
• Intervention / Treatment: Device: Transcranial direct current stimulation

• Study Type: Interventional
• Enrollment (Actual): 28
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Alabama
    • Fort Rucker, Alabama, United States, 36362
      • U.S. Army Aeromedical Research Laboratory

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 40 years (Adult)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: All

Description

Inclusion Criteria:

1. Must be 18 (if active duty), 19 (if non-active duty) up to 40 years old.
2. Must have normal hearing, vision or corrected to normal vision, and cognitive function as determined by self-report and screening by study physician
3. Must have obtained at minimum 6 hours of sleep prior to data collection, as assessed by actigraphy data and self-report.
4. Must have refrained from consumption of caffeine, 16 hours, nicotine, 2 hours, and alcohol, 24 hours, prior to the study, assessed by self-report.

Exclusion Criteria:

1. The following medically-related exclusionary criteria will be used, as assessed and verified by the study physician:

   1. Haven taken any medications which induce drowsiness, such as over-the-counter antihistamines within 24 hours of participation in the study. Any self-medication will be assessed through self-report
   2. No current medical conditions or medications affecting cognitive function or attention.
   3. Any history of any attention deficit condition requiring medication.
   4. Any history of psychological/psychiatric disorder.
   5. Any history of seizures, migraines, or neurological disorders.
   6. History of a head injury involving loss of consciousness.
   7. Any metal implanted within the head (e.g., shrapnel, surgical clips) or any implanted devices (e.g., cardiac pacemaker, brain stimulator, hydrocephalic shunt).
   8. Skin condition on the scalp, such as psoriasis or eczema, or wounds on the head.
   9. Currently receiving hormonal therapy treatments, other than birth control or as determined by physicians.
   10. Potential for caffeine withdrawal symptoms that will impede cognitive testing.
2. Females with a known pregnancy, who test positively for pregnancy, or refuse the test will be excluded, given the lack of available research regarding the effects of tDCS during pregnancy. Known pregnancy will be assessed during screening, females without a known pregnancy will be requested to provide a urine sample during the screening procedures to ensure the absence of pregnancy.

Study Plan

How is the study designed?

Design Details

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

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Active anodal stimulation; active anodal stimulation at F3, cathode placed on contralateral bicep	Device: Transcranial direct current stimulation; Transcranial direct current stimulation (tDCS) is a form of non-invasive brain stimulation that stimulates the brain through the application of a low-intensity electrical current, typically ranging from 1 to 2 milliamps (mA), via electrodes placed on an individual's scalp. During the active stimulation sessions, 2 mA of stimulation will be applied for 30 minutes. During the sham stimulation session, 2 mA of stimulation will be applied over the course of 90 sec, the electrodes will remain in place for the 30 minute duration.
Experimental: Active cathodal stimulation; active cathodal stimulation at F3, anode placed on contralateral bicep	Device: Transcranial direct current stimulation; Transcranial direct current stimulation (tDCS) is a form of non-invasive brain stimulation that stimulates the brain through the application of a low-intensity electrical current, typically ranging from 1 to 2 milliamps (mA), via electrodes placed on an individual's scalp. During the active stimulation sessions, 2 mA of stimulation will be applied for 30 minutes. During the sham stimulation session, 2 mA of stimulation will be applied over the course of 90 sec, the electrodes will remain in place for the 30 minute duration.
Sham Comparator: Sham stimulation; sham stimulation that will be counterbalanced between subjects such that half will receive sham stimulation configured as condition 1 (anode F3, cathode bicep) and half will receive condition 2 (cathode F3, anode bicep)	Device: Transcranial direct current stimulation; Transcranial direct current stimulation (tDCS) is a form of non-invasive brain stimulation that stimulates the brain through the application of a low-intensity electrical current, typically ranging from 1 to 2 milliamps (mA), via electrodes placed on an individual's scalp. During the active stimulation sessions, 2 mA of stimulation will be applied for 30 minutes. During the sham stimulation session, 2 mA of stimulation will be applied over the course of 90 sec, the electrodes will remain in place for the 30 minute duration.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Military task performance	Patrol exertion multitask	Folllowing stimulation; task lasts approximately 20 min
Military task performance	Target acquisition	Folllowing stimulation; task lasts approximately 40 min
Cognitive function - Selective Attention	Stroop test	Approximately 3 minutes during stimulation
Cognitive function - Multitasking/Working Memory	Dual n-back	Approximately 5 minutes during stimulation
Cognitive function - Working Memory	Digit span task	Approximately 2 minutes during stimulation
Cognitive function - Sustained attention	Rapid Visual Information Processing Task	Approximately 7 minutes during stimulation
Cognitive function - Executive function	Shifting Attention Task: Digit symbol substitution task	Approximately 2 minutes during stimulation

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Cognitive function - Impulsivity/Motor Control	Stop signal task - response inhibition	Approximately 3 minutes after stimulation
Cognitive function - Risk Taking/ Decision Making	Delayed Discounting Task	Approximately 1 minute after stimulation
Cognitive function - Cognitive Flexibility	Uses Task	Approximately 5 minutes after stimulation

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Confounding factor - Sleepiness	Karolinska Sleepiness Scale	Approximately 1 minute, before and after stimulation
Confounding factor - Circadian typology	Morningness-Eveningness Questionnaire	Approximately 15 minutes during intake
Moderator variable - Intelligence	Shipley's Institute of Living Scale	Approximately 15 minutes during intake
Moderator variable - Trait motivation	Behavioral Avoidance/ Inhibition Scales	Approximately 10 minutes during intake
Side effects - mood symptoms	Profile of Mood States - Short Form	Approximately 3 minutes before and after stimulation
Side effects - Physical side effects	Symptom Checklist	Approximately 2 minutes before and after stimulation
Side effects - Physiology/health	Welch Allyn Connex 6000	Approximately 5 minutes before and after stimulation

Collaborators and Investigators

• Sponsor: United States Army Aeromedical Research Laboratory

Study record dates

Study Major Dates

• Study Start (Actual): December 12, 2019
• Primary Completion (Actual): June 1, 2021
• Study Completion (Actual): September 30, 2021

Study Registration Dates

• First Submitted: November 5, 2019
• First Submitted That Met QC Criteria: November 5, 2019
• First Posted (Actual): November 7, 2019

Study Record Updates

• Last Update Posted (Actual): January 25, 2022
• Last Update Submitted That Met QC Criteria: January 24, 2022
• Last Verified: January 1, 2022

More Information

Terms related to this study

• Other Study ID Numbers: USAARL 2018-002; M-10782

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No