This protocol is adapted to our lab environment based on a protocol developed by Farrens, J. L., Simmons, A. M., Luck, S. J., & Kappenman, E. S. (2019). We are very grateful for their help and guidance.

Everyone administering EEG in the lab should read the full protocol by Farrens and colleagues. It covers additional (and important) details that are not addressed below.

Recruitment

See Instructions for recruitment document. RICHARD TO MAKE...

Prior to Participant’s Arrival

Send a reminder email 1-2 days before the study.

Here is a template for the email. This email may need updated depending on your study design:

Subject: Reminder: EEG Study Participation


Dear [Name],

Thank you for your interest in participating in the EEG study. This is a friendly reminder regarding the details of the study.

* Date and time: [Participant’s agreed date and time from the recruitment process]
* Location: Kerr 161
    * Based on the study design, it is important to arrive at the location at the specified time to avoid seeing the person you will be partnered with.
* Study duration: approximately 2 hours 
    * Please note, if you have an important event immediately after the testing session, it may be better to reschedule.
* The procedures require us to put gel in your hair, which may get on your clothing. Do not wear any clothing that may be harmed by the gel, or you would not wish to get gel on (although the gel is water soluble).
* Participants need to be completely awake during the experiment, so please have sufficient sleep before arriving.
* Please arrive with clean, dry hair, and remove all ponytails, braids, wigs, extensions, hair clips, hats, etc., prior to arrival.
If you have any questions or need further information, please feel free to reach out.

Best regards,
[Name]
[Contact Information]

Test run/record the game platform and EEG software

Move the USB bluetooth dongle into the soundbooth (the USB hub at the base of the monitor) to ensure strong connection.

Ensure all necessary equipment is prepared. Note any supplies that are low, exhausted, nearing their expiration date, and/or are damaged and contact Richard immediately to re-order.

This includes:

1. Syringe with electrode gel x 3 (short hair participants might just need 2)
2. Gauze pad for chin (for participant comfort, if necessary) 3 .Surgilast (for cap placement, if necessary)
3. Soft measuring tape
4. Gloves
5. Shampoo, clean towels, and hair dryer
6. Plastic combs
7. Alcohol wipes
8. Envirocide (for sanitizing EEG cap, combs, and cleaning toothbrushes)
9. Clorox wipes (for sanitizing sink)
10. Landry detergent and bleach (for sanitizing salon towels)
11. Swiffer wipes (for cleaning floor)
12. Hand sanitizer
13. Eye drops (if participant eyes get dry)
14. Snacks and water (for participant comfort)

During the Study

Cap/Electrode Application

Prior to the study, review and familiarize yourself with our lab's guide on [EEG Setup, Capping, and Impedance Checking](https://github.com/cogcommscience-lab/lab-docs/wiki/EEG-Setup,-Capping,-and-Impedance-Checking.

To cap a participant, follow these steps:

• Obtain consent according to the procedure approved by the IRB.
• Seat the subject in a comfortable low-backed chair in the preparation area.
• Have the subject comb their hair using a plastic comb, instructing them to concentrate on their scalp. The purpose is to loosen up some of the dead skin on the scalp, which will help reduce electrode impedances.
  • If the subject arrives with wet hair or is sweaty, have them dry their hair with the hair dryer before beginning.
  • If your subject arrives with a ponytail, braid, wig, barrettes, hair clips, or extensions of any kind, they must be removed before continuing.
• Put on a pair of gloves.
• Measure the circumference of the subject’s head using a soft tape measure, ear-to-ear (cm) circumfrence to define the measurement axis. Select the cap that best fits your subject.
• Get the MBT O smarting pro 32 EEG cap and the amplifier (don’t put in yet)
• Wear the EEG cap from front to back, like a swimming cap. Use the soft measuring tape to ensure the cap is centered. Make sure the cap does not block the ears (there are two holes for the ears). To readjust the cap, use both hands to slide or push the straps (around the ear area) into place; avoid pulling the cap into place, as this can stretch the cap and damage the electrodes. Once the cap is centered front to back, visually check that it is also centered side to side. Important notes to improve capping:
  • Part participant’s hair down the middle.
  • Cap's fabric should start two fingers above the brow bone (nasion).
  • Central line of cap must be aligned with the center of the head.
  • Secure amplifier casing onto the cap before putting it on the head.
  • Strap the chin strap securely.
  • Place the Cz electrode halfway between the nasion (brow bone) and inion (bump at back of skull).
• Once the cap is centered, have the subject close the chin strap to prevent the cap from moving (make sure it is not choking the participant). If the subject finds the chin strap uncomfortable or itchy, place a small piece of sterile gauze between the strap and the subject’s chin.
• Begin filling each electrode with gel. To do so, hold the electrode in place with the index finger and thumb of your non-dominant hand. With your dominant hand, insert the syringe tip through the notch at the top of the electrode. Ensure the syringe is in contact with the scalp, then swirl it around 3-4 times in a wide circular motion, gently pushing the hair out of the way and removing the top layer of dead skin cells. (During this process, you may squeeze a small amount of gel first and use it as an exfoliator as well.) To fill the electrode with gel, push down on the plunger while slowly pulling the syringe up and out of the electrode. This will create a smooth column of gel rather than a large glob at the bottom, reducing the potential for bridging (especially in high-density recordings). Fill the electrodes in a systematic order to avoid skipping any. Avoid placing your hand on top of any previously filled electrodes while holding the one you are currently working on in place. Be sure to fill the ground electrode.
  • The syringe tips can be intimidating to subjects. It is good to show the subjects that the syringes are not actually sharp by poking the palm of your glove-covered hand a few times. Let them know that the procedure should not be painful in any way, and if it becomes uncomfortable at any time they should let you know immediately.
• Follow these steps for checking electrode impedance and connecting the amplifier

Running a Subject

• After checking all electrodes are filled with gel, take the subject into the testing room, leaving their backpack, purse, cellphone, etc. outside the testing room and placed in one of the lab's lockers.
• Have the subject sit with their feet flat on the floor and their bottom all the way to the back of the chair. Adjust the chair height so the subject is sitting with their knees bent at a comfortable angle (~90°), and then adjust the height of the monitor on the height-adjustable table so that the center of the screen is level with their eye gaze.
• Verify that all electrodes are getting good signals on the EEG software. This includes checking the impedance level. Any electrodes over 50 kΩ (showing red on the software) needs to be adjusted.
  • Ideally, make sure all impedances are below 10 kΩ (green), but up to 30kΩ (yellow) is acceptable if stable. For any electrodes with higher impedances, reduce the impedance by inserting your syringe tip, making sure it is contacting the scalp, then re-swirling it a few times. If that does not work, try adding a bit more gel. Do not add more gel first, as this increases your risk of bridging between electrodes, especially in high density recordings. P.S. For experiments in which data quality is exceptionally important (e.g., ERP decoding experiments), reduce the impedances to <10 kΩ when possible without causing significant discomfort.
• Show the subject their EEG signals. Describe common movement artifacts, how to prevent them, and why they matter. This helps the subject understand why they are being asked to minimize certain behaviors and allows you to ensure that all artifacts are easily identified with the placement of the electrodes.
  • Eyeblinks: Ask subjects to look at the center of the recording screen and to blink 4-5 times in rapid succession. This shows them what their blinks look like and, depending on your task, why you may need them to withhold their blinks until certain time points (e.g., after their response on each trial).
  • Concentration Face: Ask the subject to clench their teeth and furrow their brow. This demonstrates the most common artifacts caused by a subject’s "concentration face." Remind the subject that it is important to keep their face, jaw, and neck as relaxed as possible throughout the experiment to help minimize this muscle noise.
  • Chewing: Ask the subject to pretend to chew gum. This demonstrates why it is important for them to completely finish eating their snack(s) before beginning the next block of the task. It is also a good opportunity to make sure your subject is not chewing gum before beginning.
• Check the temperature of the room and the lighting level. Verify that temperature, humidity, and lighting level are consistent across participants and sessions.
• Explain visual monitoring set up to the subject. You will be watching them through the webcam.
• Explain the task to the participant. Reiterate any special EEG artifact instructions like maintaining fixation or withholding blinks until a certain time. Assure the subject that there are many breaks throughout the experiment and they are free to move around as much as they need to during those portions of the experiment. However, before beginning the task again, they must return to a still and relaxed position.
• It is also best practice to save several smaller recording files rather than one long file, and break periods provide a good opportunity to start a new recording. This will prevent losing as much data if something goes wrong during the recording, and it also gives you the opportunity to check impedances during the breaks.

Recording Data

• To begin recording the EEG, hit the “Start Streaming” + “Start Recording” button. Start your recording approximately 10 seconds before the task begins and end the recording approximately 10 seconds after the task ends. This minimizes edge artifacts when filtering the EEG data offline.
• Monitor the EEG data closely at all times. Do not read books or journal articles, do homework, look at websites, read email, send texts, etc. In most cases, the experimenter should not have their cell phone nearby, which reduces the temptation to engage in distracting activities.
• Make sure all stimulus event codes and response event codes are present on the EEG software recording screen.
• Check behavioral performance continually to ensure that the participant understands the instructions, is complying, and is not becoming drowsy or unmotivated (e.g., is keeping their eyes open and fixated on the screen, etc.).
• If you see evidence of a problem with the recording (e.g., excessive noise, excessive artifacts, etc.), fix the issue as soon as possible. Depending on the task and the type of problem, this can be accomplished at the next break, or it may be beneficial to pause the task to address the issue before continuing.
• If a participant is unable to perform the task with an appropriate level of accuracy or without excessive artifacts, terminate the session early and document the issue(s).
• Regularly check the subject video camera monitor to make sure that the participant is behaving appropriately (e.g., feet still flat on the floor, remaining still, maintaining fixation, etc.).
• If the participant is becoming drowsy (as evidenced by poor task performance, excessive alpha waves, or visibly nodding off), offer the subject a snack or beverage. Turning the lights to full brightness and allowing the subject to stand and stretch their legs at the next break can also help alleviate drowsiness.

After the study completes

• Using both hands, remove the amplifier with your thumb and forefinger, then plug it back into its charger.
• Walk the subject back to the preparation area. Release the chin strap, and gently place the EEG cap aside for later cleansing.
• Clean the subject’s hair in whatever way they want (wet towel, simple rinse, full hair wash, etc.), then compensate the subject and allow them to leave (record their signature if the department needs it). Don’t make them wait while you clean everything up.
• Follow these steps to clean and sanitize EEG equipment and sink