1. Have the participant read and sign the consent form. Ask them if they have any questions, and answer them.

  2. Administer both eye tests:
  • For acuity, have participant stand on duct tape line and read the 10/20 line of letters.
  • For color vision, show them the Ishihara color book and ask them what numbers they see. If they get the first 5-7 correct, then they have normal color vision.
  1. Measure the participant’s head for cap size
  • Measure from between eyes (nasion) to inion (bony protrusion) on the back of participant’s head in cm.
  • Round down for sizes (ex- if their head measures 55, round down to a size 54 cap)
  1. Clean the participant’s upper forehead and behind the right ear
  • Wipe with alcohol prep pad, use a small (pea sized) amount of exfoliator, then wipe with alcohol pad again.
  • Use the alcohol pad to clean the side and underside of right eye. Do not exfoliate around eyes as skin is very sensitive here
  1. Plug electrodes into cap
  • Place the correctly sized cap on head model
  • Find the green or yellow/orange sticker on the splitter boxes. These will correspond with the green and yellow slots on the cap.
  • Very Important the electrode wires are very fragile. You should never pull on them and should always move the electrode from the head!
  • Holding the electrode by the head, slide it into the correct slot. Make sure to pay attention to green versus yellow colors, and for tricky numbers like 6 versus 9.
  • Ensure that all wires are facing backwards and that no wires are under tension. The electrodes can be rotated in the cap if necessary to achieve this.
  • This process takes 5-10 minutes. You may tell the participant that it’s a good time for a bathroom break, to get a drink of water, or to relax.
  1. Pleace the green and blue electrodes near the participant’s right eye, with the black electrode behind the right ear.
  • Rip off three 1-inch pieces of medical tape
  • Squirt a small amount of gel into the cavity of the green or blue electrode, and place it either on the bone underneath the right eye, or directly to the side of the right eye. Secure the electrode with tape.
  • Place the remaining green or blue electrode in the same fashion in the other eye location.
  • Using the same technique, place the black electrode on protruding bone behind participant’s ear (mastoid bone). Make sure that it is over bone, rather than jaw muscle.
  1. Place the electrode cap on the participant
  • You may want two people to do this with one person placing the cap and the other holding the cables.
  • Have someone look the participant straight on to see if the cap is centered. Measuring the distance between the ground electrode and each eye may be helpful. If you need to move the cap more than a cm, it might be worth taking the cap off and trying again.
  • To finish centering it, measure from between participant’s nasioneyes, up their forehead and to their inion. Divide this measurement in half and move cap until the blue port is aligned with half the measured difference. For example, if the distance between the eyes and inion is 34 cm, you would line the blue port on top of the cap so that it lays at 17cm from nasion.

  1. Instruct the participant to secure chin straps, watching to ensure that wires don’t get caught in the straps.

  2. Ask participant if they are okay with the electrode boxes being clippedhooked to their shirt. If not, wait until you get into the experimental room and use duct tape to fix splitter boxes them to their chair. Note: because the chair back is fairly low, this will restrict participant’s mobility considerably.

  3. Have the participant stand up to walk to the experimental room. Follow behind them holding all cords and wires. Ask the participant to adjust the chair so that they are at a comfortable typing distance from the keyboard. Note: many participants will sit too far back, so encourage them to sit closer to the computer so that shoulder muscle tension doesn’t show up on the recording.

  4. Bring EEG machine and laptop into the experimental room.
  • Use black and red connector cable to plug the EEG amplifier into the power source
  • Laptop may be plugged into power strip while setting up, but should be unplugged while recording
  1. Plug in all cables
  • Ground electrode goes in GND
  • Green electrode ribbons are plugged in the top slot that is nearest to the participant, with the yellow/orange ribbons in the second row.
  • Plug the photocell into AUX1
  • Plug the eye electrodes into AUX2
  • All cables will snap into place when properly placed. AUX and GND cables have a notch that indicates where the top is. Do not force cables - if something doesn’t seem to fit, please ask!

  1. Start matlab and set the path to Psychtoolbox (/User/Shared/)

  2. Correct the EEG machine to the recording laptop via USB

  3. On the recording laptop, click on Pycorder software. Accept the warning message.

  4. Enter impedance mode and begin to gel electrodes.
  • Electrode lights go from red (bad connection) to green (good connection), with a yellow light indicating a “meh” connection. We will not record until all electrodes are green.
  • Always gel the ground electrode first. If it doesn’t turn green right away, you may move on to others, but it’s important for there to be gel here before any of the other electrodes will connect.
  • Most of the activity is in moving the hair. You do not need as much gel as you may think.
  • Use circular motions to move hair out of the way, and then squirt a small amount of gel into the well. Holding an electrode against the scalp for a few seconds can really help get a good connection.
  • Make sure to keep checking in with the participant about if there are sensitive areas on their scalp that should be avoided, if your pressure is okay, etc.
  • Tell the participant to open a browser and watch YouTube videos, read the news, check Twitter, etc. to help time pass. Depending on how cooperative their scalp is, the process can take between 15 and 60 minutes.
  • If an electrode is being stubborn, move on and come back to it and/or check the impedance value for the ground electrode and adjust as needed (if the number is high, try to work on the electrode a bit and get its impedance down, that will help all of the other electrodes).
  • If the cap is baggy and several nearby electrodes are difficult, consider using the pre-wrap to put pressure on all of them.
  • Continue gelling until all electrodes are green. Look at the impedance values on the recording laptop. In an ideal world, these will all be under 10.

  1. Once we are happy with the impedances, switch the laptop to default mode and scroll through each group of electrode waveforms, look to see if any look crazy/abnormal. Note: it takes a full 10-20 seconds for all waveforms to show. If 1-2 electrodes look noisy, adding a little more gel or moving hair again can help. If all/most electrodes look noisy, muscle tension is often to blame. Ask the participant to relax, and make sure their legs are uncrossed.

  2. When you are happy with the waveforms, hit ‘start recording’ on the laptop and name your participant file based on the naming convention for that study.

  3. Execute the code for your study on the experimental computer.

  4. Stay with the participant during the experiment. Scroll through the waveforms occasionally to ensure that no electrodes go crazy during recording, and watch the participant for extraneous movement that can cause a noisy recording, or for falling asleep.

  5. Keep in mind that all of the following can affect noise level:
  • Sweat. There’s not too much we can do about this except keep the lab cool. :)
  • Eye blinks/any muscle movement, encourage your participant to sit still while completing the task and then move around during the breaks. Eye blinks can be taken care of while preprocessing the data later on, so they shouldn’t be focusing too much on it, but if they are blinking a lot then it can make the data noisy.
  • If they cross their legs this can cause some weird stuff to happen, I have seen a participant have just their feet crossed and it made all of their data look crazy. Encourage participants to keep their feet flat on the ground.
  • Shaking legs/fidgeting can really make things look strange, encourage your participant to take longer breaks during the designated break time to get out their energy/stretches/fidgeting so that they are not doing that during the experimental blocks.
  • Stress and muscle tension (like clenching one’s jaw) can show up as high frequency noise. This is why it’s good to keep participants happy with upbeat conversation, funny YouTube videos, etc.

  1. When the study has been completed, end the recording and remove the cap and face electrodes from the participant.

  2. Provide participant with debrief form and try to answer any questions they may have about the study. If they are participating for money, pay them and have them sign a sheet as a record of payment. If they are participating for credit, get the name of their psychology/neuroscience professor and fill out the form right away.

  3. IMPORTANT: Move the EEG machine back to it’s home and plug in the power supply. The battery life of the power supply depends on it being plugged in most of the time, the opposite of how most batteries work.

  4. Get the EEG data files transferring to etna. Make sure that all three files that are created are transferred.

  5. Clean up! Fill both bins with warm water, pour a very small (i.e. a few drops) amount of barbicide into the bin labelled “cap”, and wash the cap and electrodes gently with toothbrushes in the designated bins. Be careful not to get water on the splitter boxes. Cover these with a towel at all times.

  6. Run the electrodes under running water in the sink, being careful to keep the splitter boxes dry. Rinse the cap until water runs clear.

  7. Hang cap and electrodes in window to dry, making sure that cables are not under pressure, and that nothing wet is on the electrode splitter boxes.

  8. Repeat all steps, and repeat, and repeat, and repeat!