Unilateral M1 Anodal tDCS to Enhance Learning in a Gross Movement Videogame Task

The study will utilize a between-subjects, SHAM controlled design. Subjects will be randomly selected to receive either SHAM (n=26) or a-tDCS (n=26) stimulation and will be blinded to their condition throughout testing.

Subjects will complete a total of two testing sessions (two study visits or days), separated by ~24 hours. Both sessions will have the subject play the videogame "Beat Saber", with a single song done for several trials as pre- and post-assessments. The first session will contain a 20-minute practice/stimulation block where subjects practice playing a song on Beat Saber while receiving either "active" or "inactive" stimulation of the motor cortex. The first session will last approximately 75 to 90 minutes whereas the second session will last approximately 15 to 20 minutes.

After providing informed consent, the subject will be given basic instructions by the researchers on how to use the VR headset and controller. Subjects will then be allowed to play the test song one time on the video game as a familiarization trial. The test song is approximately 4 minutes in length. Upon completing the familiarization trial, the subjects will then perform 2 more test song trials with 3-minute rest between each to minimize fatigue. The performance of these two trials will be averaged and that will serve as the pre-assessment measure.

After the pre-assessment, the skull will be measured and researchers will follow standard procedures for determining the correct stimulation spot for the index finger muscle, the first dorsal interosseus (FDI), which is a common muscle used in tDCS due to the large cortical representation. Following that, electrodes will be placed for stimulation and the 20 minute practice period will begin.

The practice phase will consist of performing 3 practice test song trials while concurrently receiving a-tDCS or SHAM. A Soterix 1x1 tDCS unit will be used to deliver anodal current through M1, of the opposite hemisphere to the VR controller hand, with a 30-second ramp up to 1 mA followed by 20 minutes of continuous stimulation in the a-tDCS condition. The SHAM condition will simulate stimulation by administering a 30 second ramp up to 1 mA followed by an immediate shut off. When the 20-minute practice session concludes, the tDCS electrodes will be removed and the subject will repeat the same procedures (2 trials) as the pre-assessment, and this will be considered the post-assessment.

In a second session, the subject will visit the lab for a brief follow-iup by completing 2 song trials, the exact same as the pre- and post-assessment.

Inclusion criteria

• · Healthy adults between the ages 18-45

• Answer 'no' to questions 2 through 18 on the tDCS checklist as these factors can increase likelihood of adverse events with tDCS (Appendix 1)

• No neurological damage, disease, or dysfunction (nerve damage, chronic pain disorders, diabetic neuropathy) that affect the upper limbs.
• No significant acute or chronic medical, neurologic, or illness in the patient that, in the judgment of the Principal Investigator, could compromise subject safety, limit the ability to complete the study, and/or compromise the objectives of the study

Exclusion criteria

• · Currently prescribed and taking stimulant medication (Adderall, Ritalin, Vyvanse, etc.)

• Consumption of over-the-counter stimulants such as caffeine or nicotine (coffee, soda, supplements, energy drinks, tobacco products, or other nicotine containing products such as gum, vape pens, etc...) 12 hours prior to entering the lab on the day of testing as this can directly affect cortical excitability. If a subject takes any of these substances 12 hours prior to session 1 they will be asked to reschedule for a later date.
• Have played the game Beat Saber on a Virtual Reality Headset in the last 12 months.