What this trial measures

• Symbol Digit Modalities Test (SDMT)Baseline, 1-week post, & 6-weeks post intervention

  Standardized neuropsychological assessment measure of visual attention and working memory

• Neuropsychological Assessment Battery (NAB) Attention ModuleBaseline, 1-week post, & 6-weeks post intervention

  Standardized neuropsychological assessment consisting of 4 subtests to assess visual and auditory attention, working memory, and scanning

• Neurobehavioral Symptom Inventory (NSI)Baseline, 1-week post, & 6-weeks post intervention

  A measure of common post-concussive symptoms rated on a 5-point Likert scale (0-4); with low scores corresponding to mild or no incidence of symptoms and high scores corresponding to more severe incidence of symptoms.

• Electroencephalogram (EEG) - Resting State Functional ConnectivityBaseline, 1-week post, & 6-weeks post intervention

  Resting State EEG will be collected to assess neural dynamics or functional connectivity and spectral power of delta,theta, alpha, beta, and gamma frequency bands.

• Electroencephalogram (EEG) - Resting State Spectral PowerBaseline, 1-week post, & 6-weeks post intervention

  Resting State EEG will be collected to assess spectral power of standard frequency bands (delta, theta, alpha, beta, and gamma).

• Magnetic Resonance Imaging (MRI) - T1 (optional)Baseline & 1-week post intervention

  MRI will be used to collect a T1-weighted (structural scan) pulse sequence of the brain.

• Magnetic Resonance Imaging (MRI) - T2 (optional)Baseline & 1-week post intervention

  MRI will be used to collect a T2-weighted pulse sequence of the brain.

• Magnetic Resonance Imaging (MRI) - T2* (optional)Baseline & 1-week post intervention

  MRI will be used to collect a T2\*-weighted (BOLD-contrast fMRI / Resting State) pulse sequence of the brain.

• Magnetic Resonance Imaging (MRI) - DWI (optional)Baseline & 1-week post intervention

  MRI will be used to collect a Diffusion Weighted Imaging (DWI) pulse sequence of the brain (white-matter tractography).

• Magnetic Resonance Imaging (MRI) - ASL (optional)Baseline & 1-week post intervention

  MRI will be used to collect an Arterial Spin Labeling (ASL / Blood Flow Rate) pulse sequence of the brain.

• Magnetic Resonance Imaging (MRI) - ROI Analysis (optional)Baseline & 1-week post intervention

  T2\*-weighted (Resting State) images will be analyzed with Region of Interest (ROI) time-courses to generate a partial correlation value (Fisher Z) that depicts functional connectivity.

• NIH Toolbox Quality of Life Assessment (NeuroQoL)Baseline, 1-week post, & 6-weeks post intervention

  Questionnaire to assess quality of life with regard to cognitive, social, emotional, and behavioral abilities rated on a 5-point Likert scale (1-5); with low scores corresponding to mild to no impairment in these abilities and high scores corresponding to more severe impairment in these abilities.

• Insomnia Severity Index (ISI)Baseline, 1-week post, & 6-weeks post intervention

  Measure of insomnia severity rated on a 5-point Likert scale (0-4); with low scores corresponding to mild or no incidence of insomnia and high scores corresponding to more severe incidences of insomnia.

• Patient Health Questionnaire (PHQ-8)Baseline, 1-week post, & 6-weeks post intervention

  The PHQ is a self-report inventory that is used as a screening and diagnostic tool for depressive disorders using a 4-point Likert scale (e.g., 0 = not at all, 3 = nearly every day), yielding a total score from 0 - 21. The eight-item Patient Health Questionnaire depression scale (PHQ-8) is established as a valid diagnostic and severity measure for depressive disorders in large clinical research studies.

• PTSD Checklist- Civilian Version (PCL-C)Baseline, 1-week post, & 6-weeks post intervention

  A 17-item self-report rating scale used as a screening tool for posttraumatic stress disorder (PTSD) using a 5-point Likert scale (e.g., 1 = not at all, 5 = extremely), yielding a total score from 17 - 85. This version asks about symptoms in relation to generic "stressful experiences" and can be used with any population. It simplifies assessment based on multiple traumas because symptom endorsements are not attributed to a specific event. Importantly, the PCL-C has been established as a valid measure of PTSD severity in Active Duty Service Members and Veterans.

• Patient Global Impression of Change (PGIC)1-week post & 6-weeks post intervention

  This scale evaluates all aspects of patients' health and assesses if there has been an improvement or decline in clinical status. Specifically, individuals are asked to calculate the difference between their current and previous health state based on a Likert scale. They are required to answer the question "Since beginning treatment at this clinic, how would you describe the change (if any) in activity limitations, symptoms, emotions, and overall quality of life, related to your painful condition." Score ranges from 1 (no change or condition got worse) to 7 (a great deal better). They are then required to circle a number between 0 to 10 that reflects the degree of change since the start of the intervention. The test takes approximately 2 minutes to complete.

• Information Sampling Task (IST)Baseline, 1-week post, & 6-weeks post intervention

  A test of reflection impulsivity. It presents a series of trials with an array of 25 grey boxes arranged in a 5x5 matrix. The grey boxes conceal yellow or blue squares on each trial. The subject decides which of the two underlying colors (yellow or blue) lay in the majority. The subject can open as many boxes as they wish to make a decision. Correct decisions are awarded a number of points.

• Groton Maze Learning Task (GMLT)Baseline, 1-week post, & 6-weeks post intervention

  A cognitive test of spatial working memory and error monitoring that has been shown to be sensitive to detecting longitudinal change in cognitive ability.78 It consists of a 10 x 10 grid of grey tiles. To complete the maze, the participant must click on the tiles to follow a hidden pathway through the grid from the top left corner to the bottom right corner. They must only click on adjacent tiles, and return to the previous tile if an error is made before moving on. The participant receives visual and auditory feedback for correct and incorrect moves. There are various types of errors (e.g., perseverative error, rule-break error) recorded depending on which type of rule has been broken, and the time to complete the maze is recorded. The trial ends once the participant reaches the bottom right corner of the grid of tiles.

• Fusion Task: BEAMBaseline, 1-week post, & 6-weeks post intervention

  For the BEAM subtask, the subject will be directed to change his/her fixation from a crosshair displayed at the center of screen to a white circle appearing randomly on the left or right side of the screen. The subject will press a button labeled either "Left" or "Right" based on whether the circle appeared on the left or right of the screen. In a small percentage of the trials in which a red arrow appears in the center of the screen, the subject will be instructed not to look at the circle nor press any buttons (inhibition test). Saccadic eye movements, pupil responses, and manual response time (RT) in addition to errors will be recorded.

• Fusion Task: N-BackBaseline, 1-week post, & 6-weeks post intervention

  For the N-Back subtask, the subject will be directed to change his/her fixation from a cross sign displayed at the center of screen to a colored circle (Green or Blue) that randomly appears on the left or right side of the screen. In the first, '0-back' condition, the subject shall push a response button labeled either (1) "GREEN" or (2) "BLUE" in accordance with the color of the circle currently on the screen. In the second, '1-back' condition, immediately upon recognition of the color of the circle, the subject shall push a response button labeled with either (1) "SAME" if the color matches the circle that appeared previously, or (2) "DIFFERENT" if the color does not match. Saccadic eye movements, pupil responses, and manual response time (RT) in addition to errors will be recorded.

• tDCS Symptom Rating Questionnaire (SRQ)Assessment collected daily during the intervention block (b/t baseline & 1-week post)

  Questionnaire to assess pre-post tDCS symptom rating, rated on a 4-point Likert scale (0-3); with low scores corresponding to mild or no incidence of symptoms and high scores corresponding to severe incidence of symptoms.

• Ecological Momentary Assessment (EMA)Assessment collected daily during the intervention block (b/t baseline & 1-week post)

  A data capture technique that involves repeated sampling of thoughts, feelings, or behaviors as close in time to the experience as possible in the naturalistic environment. A series of 18 self-report questions rated on a 10-point Likert scale (Q1 - Q15) and 5-point Likert scale (Q16 - Q18) regarding mood, current cognitive state, and environment. EMA data is used to look for relationships between variables with the causal discovery analysis.