The Pittsburgh Sleep Quality Index (PSQI) subscale measurement that was used is overall sleep quality, which is derived from question 6 on the assessment and uses a Likert scale of 0 to 3. A score of 0 represents "very good" sleep quality (better outcome), while a measurement of 3 represents "very bad" sleep quality (worse outcome).

The PSQI was not administered to the HC wavelength-2 and HC wavelength-1 arms of this study.

Sleep Efficiency is the overall percentage of time that the participant was scored as sleeping during their night of sleep (range: 0-100%). Higher percentages suggest higher sleep quality and a better outcome.

Actigraphy data was not collected for the HC wavelength-2 and HC wavelength-1 arms of this study.

Wake After Sleep Onset (WASO) is how many minutes the participant, during their night of sleep, was determined to be awake after their sleep onset. Sleep onset is defined as a state of at least 2 minutes of uninterrupted sleep. Higher values indicate a worse outcome (range: 1-125 minutes).

Actigraphy data was not collected for the HC wavelength-2 and HC wavelength-1 arms of this study.

Neural activation during functional magnetic resonance imaging (fMRI) measuring executive functioning using the MSIT.

Data was collected for this measure but was unable to be analyzed due to issues extracting the data from the computer it was stored on. In addition, MSIT data was not collected for the HC wavelength-2 and HC wavelength-1 arms of this study 6-weeks after the inital visit.

The Automated Neuropsychological Assessment Metrics (ANAM) is a neuropsychological battery that uses individual tests to measure cognitive efficiency in areas including attention, concentration, reaction time, memory, processing speed, and decision making. Subscale scores are put in terms of a throughput score, which is calculated to be a ratio of correct responses per minute, as a way to measure cognitive efficiency in the participant; as such, the units for the throughput scores would be in terms of correct responses/minute. Higher throughput scores indicate increased levels of cognitive efficiency in the relevant subscale. The throughput score ranges for the ANAM subscales are:

code substitution learning: 0-147 responses per minute procedural reaction time: 0-151 responses per minute mathematical processing: 0-145 responses per minute matching to sample: 0-97 responses per minute code substitution delayed: 0-155 responses per minute

ANAM data was not collected for the HC wavelength-2 and HC wavelength-1 arms of this study.

The Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) uses all of its subscales to calculate the RBANS total score (index). To obtain the RBANS total score (index), the raw scores of the subtests must first be computed into index scores for their relevant subscale (different subtest raw scores feed into specific subscales) using RBANS specific tables that have scaled scores embedded and are normed for the age of the participant. The index scores of each subscale are then summed together to get the Sum of Index Scores, which has a possible range of 200-800. Once the Sum of Index Scores is found, the total score (index) is then found using another RBANS specific table with scaled scores embedded within it. The total score (index) has a possible range of 40-160, with a higher total score (index) is related to a better outcome.

RBANs data was not collected for the HC wavelength-2 and HC wavelength-1 arms of this study.

The Psychomotor Vigilance Task (PVT) is a task that tests alertness by having the participant press a button every time they see a stimulus image appear on a screen. This image is presented at random 2-10 second intervals throughout the entirety of the task. The reaction time (RT) is one of the PVT measurements and is the time, measured in milliseconds, that it takes for the participant to view the stimulus image and then press the button, confirming that they have indeed viewed the stimulus image at that time. The PVT measures speed using the following equation: 1/RT * 1000. The PVT measurement used here is average speed, so all the calculated speeds were then averaged over the entire trial period to obtain the final value for that trial at that time point (post-tx 1,2,3). Since the PVT is a timed measurement of reaction times, lower scores are considered 'better' or indicate an increased level of vigilance.

PVT data was not collected for the HC wavelength-2 and HC wavelength-1 arms of this study 6-weeks after the initial visit.

The Epworth Sleepiness Scale (ESS) is an 8-item questionnaire that characterizes the likelihood of the participant 'dozing off' during typical daily activities over their last 2 weeks, and uses a 0-3 point Likert scale, where 0 corresponds to "Would never doze" and 3 corresponds to having a "High chance of dozing" during the activity in question. The ESS score is calculated by adding up all the scores for each question, which means that the ESS score has a range of 0-24, while a higher score indicates that the participant had more issues with daytime sleepiness (worse outcome).

ESS data was not collected for the HC wavelength-2 and HC wavelength-1 arms of this study.

The Functional Outcome of Sleep Questionnaire (FOSQ) questions 1-26 use a 1-4 (ordinal) likert (1 = "No difficulty" with sleepiness, 4 = "Yes, extreme difficulty" with sleepiness) and the participant also has the option of putting 0 = "I don't do this activity for other reasons".

FOSQ questions 27-30 use a 1-4 Likert scale where 1 = "Very low" in terms of characterizing the level that sleepiness affects different aspects of their intimate romantic relations, while a 4 = "High" amount of impact on their intimate romantic relations.

The FOSQ total score measurement is determined by calculating the mean of all 5 subscale scores and then multiplying that value by 5 (range: 0-24). A higher score indicates that the participant had more issues with daytime sleepiness.

FOSQ was not collected for the HC wavelength-2 and HC wavelength-1 arms of this study.

The Rivermead Post-Concussion Symptoms Questionnaire (RPCSQ) will be used to assess post-concussive symptoms related to sleep. All questions on the RPCSQ use a 0 to 4 Likert scale concerning the severity of experiencing differing symptoms, where 0 = "not experienced" and 4 = "severe problem". As such, having a higher score is indicative that the participant is having more serious sleep issues related to their head injury. The RPCSQ subscale measurements that were used below are: RPQ3, which is the summed scores from the first 3 questions on the form, with the subscale total ranging from 0-12, and RPQ13, which is the summed scores from questions 4 to 16 on the form, with the subscale total ranging from 0-52. The RPQ3 subscale is associated with earlier symptom clusters of post-concussive symptoms as they relate to sleep disturbances, while the RPQ13 subscale is associated with later symptom clusters of post-concussive symptoms as they relate to sleep disturbances.

The RPCSQ was not administered to the HC wavelength-2 and HC wavelength-1 arms of this study.