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eegerp:protocols

Specified grant Protocols should be written up and linked to here.

General Protocol

Reserving the EEG lab

  1. All reservations for the EEG lab must be made online through the Haskins website. You need a username to make reservations. See Mike D’Angelo dangelo@haskins.yale.edu for setting one up, or use the generic username/password (username: eeglab, password: eeglab)
  2. Go to the Haskins homepage (www.haskins.yale.edu). On the left-hand side of the page, click on “For Employees”. On this new page, again look at the left-hand side of the screen, click on “Lab Manager”.
  3. From here you have 2 options:
    1. Ordered List Item- To book the CLS waiting room & EEG lab together, click on “Child Language Studies”. Scroll down and click “EEG Lab, Room 160”. In the top portion of the pop up window fill in: “start/end time” (make sure to give yourself a 10-15 minute buffer), “HIC number” (assigned to you by Mike when setting up your account), “Scientist” (you can put in Landi/Pugh), “email” (email of whoever will run the session. They will get a reminder email and can delete or modify the session if someone cancels), “comment” (example: “RA–your name–A40-3 EEG”. This way, people know you are running someone, not reserving for data analysis). The bottom part is to reserve the CLS waiting room; in most cases you want to select the 2nd option “Nonexclusive, traffic is ok” so other people can also use the CLS waiting room, if they are running an experiment in the CLS). If you have a large family or something, you can select “Exclusive”, which locks out other people from being able to reserve the room.
    2. Ordered List Item- If you do not need the CLS waiting room, click on “EEG lab” to make the reservation in the same manner listed above, without reserving the CLS waiting room. In most cases, you want to reserve the rooms together.
  4. To modify an existing session, you must delete the session and create it again. Go to “Lab Manager” then click on either “Child Language Studies” or “EEG Lab”, then click the name under “Scientist”. When asked if you want to delete the session, click “yes” then make a new session. Make sure to delete/modify the reserved sessions from the calendars, to free up the calendar for other groups.
  5. Reserve the EEG lab as soon as you have someone scheduled. This is a shared space and other people will be making appointments. Make sure you mark these appointments on your own calendars as well shared calendars (YRC calendar, Google Cal, etc), so you do not overbook. Try to reserve the lab for an hour longer than the experiments length, so you do not need to worry about being pressed for time.

Lab Preparation

Before the EEG

  1. The day before the EEG, it is important to let the participant (and/or parent) know exactly what to expect from the EEG scan. When contacting them, explain the task to them a bit (what the participant will be doing, how long it will take, where to meet, etc); this will help put the participant (and parent) at ease.
  2. On the day of the scan, meet the family @ CLS 20-30 minutes before start of scan. This allows time for filling out paperwork, taking care of parking, and prepping the EEG (see next section). Also, use this time to remind the participant what will be going on during the EEG scan.
  3. Turn on the EEG Mac the E-Prime PC. If you are using Eye Tracking, refer the instructions below.
  4. Set-up the DVD player (in black cabinet) if needed. Make sure the DVD player is plugged into a power strip (near the mac tower) and not the wall. It will cause the signal to be very noisy if plugged into the wall.
  5. Show participant the waiting room and the EEG lab. Have the participant wait in the waiting room while getting set up for the EEG.
  6. Measure the circumference of the participant’s head in cm. Do this in the beginning so you can pick the correct cap size and soak it in the electrolyte solution while the participant is filling out paperwork, to save time.
  7. Make the electrolyte solution
    1. Ordered List Item- In bucket, place 1.5 spoonfuls of potassium chloride salt, mixed with a scoop of shampoo (Use the labeled measuring devices, labeled “salt”, “shampoo”, etc.) to measure out the appropriate quantities.
    2. Ordered List Item- Fill bucket so the water level (use warm water) is between “1” and “2” (1.25-1.5 is ideal). DO NOT add too much or too little water, salt, or shampoo. This will throw off the ratio for the solution.
    3. Ordered List Item- Make sure all contents in bucket are mixed well (stir as needed). Place cap in bucket, dunk in and out for 30 seconds, then let it soak in bucket for 10 minutes (set timer).
  8. Start filling out a blank EEG Checklist for the participant. Fill in ALL the details you can. Any information about what occurs during the experiment can be helpful when analyzing the data in the future.

EEG Cap Preparation

Measuring the Head

Two more measurements must be made in order to center the cap on the participant’s head.

  • Unordered List Item 1st measurement: Place the measuring tape in the middle of the participant’s forehead (between eyebrows) and run it to under the bump in the back of the person’s head. Place a notch mark at the midpoint of this total distance (i.e. total length = 37cm, place dot at 19cm). Mark the midpoint with a line.
  • Unordered List Item 2nd measurement: Places the tape at the middle of the participant’s ear, and run the tape over the participant’s head to the middle of the other ear. Take the midpoint of this distance, and place a line on the person’s head.

Make a circle or dot where the 1st and 2nd lines intersect. This is where the center of the EEG cap (REF point CZ) needs to go. Once these measurements have been made, and the cap has soaked for 10 minutes, it is time to place the cap on the participant’s head.

NOTE: Consult EEG cap placement manual, by EGI for more specific instructions.

Placing The Cap On The Head

  1. Place a towel (found in black cabinet) around the participant’s shoulders. Place another over the front of their shirt. This is to prevent water from dripping on them. Make sure the participant has removed earrings, glasses, etc. prior to putting on cap. Glasses can be placed back on the face after cap is put on.
  2. Ask the participant to close eyes while putting cap on head. This prevents excess water from going into participant’s eyes. Tell participant it should only take a couple minutes to get cap on in a comfortable spot and you will let them know when their eyes can be opened.
  3. Make sure the sponges on cap are on the inside and the circles and numbers are on the outside.
  4. Spread cap out as wide as possible with both hands (without over-stretching the cap). Start off behind the participant’s head; slowly bring the cap over the participant’s head, ensuring that the red REF reference electrode aligns with the dots made previously, which mark the center of the participant’s head. It is very important that REF rest upon the center of the participant’s head.
  5. It helps to keep your hands in the cap as long as possible, until the cap is fully in place. Make sure to line up the ear holes properly, look for electrode #17 to be between/above the person’s eyebrows, etc.
  6. If the REF electrode is more than 0.5 cm away from the center of the head, the cap must be taken off, re-soaked for 1-2 minutes, and then reapplied onto the participant’s head. The quicker the cap gets on the participant’s head, the better. Not only for comfort of participant, but also for the sake of the wetness of the sponges. It is very hard to keep sponges wet, and the more time the cap is out of the bucket; the more the sponges are drying.

NOTE: Putting on the cap is one of the trickier parts of doing the EEG. It takes some practice to master, but once you get it down, it should take only a minute or two to place the cap on correctly.

Starting the Net Station Session Once the cap is on and plugged into the amp arm you can open Net Station. Click Session; select “Haskins EEG Template”. In the subject field, where it says <Default>, delete that and enter the appropriate file name. Next click “Rename”. Save the file to the correct experiment folder and delete all the extra numbers after the appropriate file name. Click “begin session”.

Getting rid of Impedances

  1. Make sure all sponges are turned in the correct direction and making good contact with the surface of the skin (not just their hair).
  2. Once session has started, click the “Panels” tab and go to “Impedances”. In this window, click measure impedances
  3. The goal is to have all of the sponges be green (3-5 in the red, is still OK as long as impedance value is under 80, this is displayed in the measure impedance window)
  4. If there are sponges that are red, go around in a systematic fashion both scrubbing the sponges (i.e. making sure they have good contact with scalp) and also adding 2-3 drops of electrolyte solution to sponges that appear to be dry. Many times hair comes between the sponge and the scalp, causing impedances to be high. Use the pipette to part hair, to make contact with the scalp.
  5. Once satisfied with the status of the cap (0-5 sponges red, or so) click “Save and Close” in the measure impedance window. At this point you are ready to start the experiment from E-Prime.
  6. For studies with more than one experiment, re-check the impedances before starting the next experiment, as described above. The cap will inevitably dry out during the first experiment, so you need to fix as many impedances as you can before moving onto the next one. This shouldn’t take much longer than 5 minutes. Don’t take too long, because then other electrodes will start to dry out as well.

Running the Experiments

Right Before You Start

  1. Turn on the “In Use” switch to the EEG lab, so people know an experiment is in session. Turn off big light in EEG lab and turn lamplights on dim. Pull the curtain between you and the participant, so your computers do not distract them during the experiments.
  2. Make sure none of the wires or the participant is touching anything metal. Also make sure they are seated comfortably and that the back of their head is not touching the chair, this will cause problems with EEG signal.
  3. Make sure the proper stimuli/conditions are set. Sync the participant’s screen with the PC. Check that the sound (box to the right of the PC) is at the appropriate level.
  4. Open up experiment in E-Prime ONLY AFTER impedances are checked and saved.
  5. Once you have the Experiment open, click on the “purple running man” icon, and then when prompted, enter in the subject number, and session number. The session number should reflect the number of EEGs the participant has had for this experiment. Any other information should also be filled out completely.
  6. Once you have explained the task to the participant, follow the on screen instructions to start experiment and continue through the blocks/experiment.

Things to keep an eye on during experiment

  1. Check the Events in Net Station to make sure that the Experiment is recording correctly. When the Experiment begins in E-Prime, an event flags should appear in the Net station Events bar with the same name as the E-Prime File. Flags should continue to appear in Net Station at the beginning (‘bign’) and end (‘TRSP’) of every trial. If the participant is required to respond to the task make sure you see “resp” flags appear in the Events bar.
  2. You can put on filters to see clear waveforms while the experiment is running: Go to Panels, then digital filter controls. Turn On filters (in the top left of the window). Press the highpass button then select 0.5 Hz. Then press the Notch button and select 60 Hz. Play around with the amplitude value until the waves look regular (~30-40).
  3. You should scroll through the channels (1-128) every 5-6 minutes. The waves should look relatively smooth and consistent. You can click on any bad channels to highlight them red and keep an eye on them. Make a note of consistently bad channels on the EEG checklist.
  4. Some movement is normal during the scans, however, the more a person moves, or the higher the impedances, or if anything on the cap is touching metal, the noisier the EEG signal will look. If you think a person is moving too much, peek behind the curtain to see. During any breaks in the experiment check to see if the participant is comfortable and remind them to try and keep still.
  5. You will pick up other tricks, as you get better. You can play around with the tools, and figure out how you can change the amount of channels you view, also change the viewing to just look at only 13 channels at a time by clicking on the box above the channels where the lines are more spaced out.

After EEG

Stopping Programs and Saving Data

  1. E-prime should stop automatically or after you click the end screen. If Net Stations does not close automatically, click “Close Session” in the upper right hand corner.
  2. PC Data will automatically save to the experiment’s folder. For each participant you run, there should be an edat (eData) file and a txt file. Check to see that both files saved.
  3. The Net Station file will be saved in the folder that you chose when you “Renamed” the session. Go to wherever you saved the data, your Net Station.

Documenting Problems

  1. If something went wrong during the experiment or appears to be wrong or incomplete about the file document the problem on the EEG Checklist and check the troubleshooting page.
  2. Any issues can also be noted in the spotlight comments section of the Net Station file by right clicking the file, selecting Get Info.

Cleaning the Cap

  1. Cap must be rinsed in water to get out all electrolyte solution. Rinse 4 times in bucket, in a sink, while lifting and dropping cap into water. Use fresh water for each rinse. The cap doesn’t have any electrolyte solution when water does not appear cloudy/soapy.
  2. Place cap in Disinfectant bucket for 10 minutes. For first minute or so, switch the cap around in the bucket, to make sure to get solution to all sponges. Then allow the cap to sit in bucket for remainder of 10 minutes. Don’t use disinfectant that was mixed more than 2 weeks ago.
  3. After 10 minutes in disinfectant, the cap must come out. It is DAMAGING to the cap if left in for longer than 10 minutes. Immediately rinse the cap thoroughly, filling and emptying the bucket with water 4 times, as done in a previous step before placing cap in disinfectant.
  4. Hang cap on the hooks, inside out, in the EEG lab
  5. Dispose of towels in proper dirty laundry container in lab, put away DVD player and anything else that was used during EEG session.
  6. Leave the lab as you found it; turn off lights and computer, etc.
eegerp/protocols.txt · Last modified: 2015/02/18 20:48 by nina