Electroencephalography Lab Dr. David Pittman – modified 4/18/2011

One person in the pair is to serve as the subject in the EEG lab and the other person is to serve as the experimenter. You should reverse roles once you have completed the lab for one person in the pair. When you are the subject it is very important that you keep your eyes open and try to focus only on either the music or word stimuli.

Participant Set-up

• Cap Placement: Proper CAP placement is critical. Put the cap on the head with the tag in the back. You must center the cap so that the front two electrodes are centered on the subject’s forehead. Then stretch the cap back over the head until it is securely in place. You may need to adjust the cap so that it is correctly in place. To do this you need to make sure that electrode CZ is in the very middle of the head. Measure the head from inion to naison and from one preauricular (above the cartilage on ear) point to the other and divide by two to see

where CZ should be placed (see diagram). Adjust cap as needed.

• Set up Reference (ear) Electrodes: Before securing the cap chin-strap of black Velcro, attach the two ear electrodes to the ear lobe like earrings. Then use the syringe to fill the ear reference electrodes with gel using the provided. Once the

ear electrodes are in place you can carefully pull the cap over the ears and secure with the provided Velcro as a chinstrap.

• Set Up Active Electrodes (T3 and T4): First

have the participant lay down with their head on the pillow being careful to not lay on top of the EEG connecting cords. The two electrode sites that we will record from are: T3 and T4. The yellow arrow in the figure to the left is pointing at the T4 electrode site on the right side of the temporal lobe above the ear. Using the syringe, you should part the hair and scratch the surface of the scalp. You should then touch the scalp and lift the syringe

away from the head as you press the plunger. Less is more. You can always add more later. (If you hold the tip at the scalp and do not draw in upward in a column while pressing the plunger, the gel will spread across the scalp rather than forming a conductive column from the scalp to the top of the electrode). You should then wrap the strap around the head to secure the electrodes.

CHECK THE ELECTRODE CONNECTIONS

• T3 & T4: The electrode lead for T3 (left-side temporal electrode) is coded with a violet wire and a white tip and the T4 (right-side temporal electrode) is coded with a violet wire and red tip. These should already be plugged into the red dot (VIN+) input on left (L) and right (R) electrode leads. These leads are connected to the BIOPAC MP36 for the NEURO9 computer (see the below image). You will need to make sure that the T3 lead is plugged into the CHANNEL 1 location and T4 is in CHANNEL 2 of the BIOPAC hooked up to NEURO9.

• Ground: The ground wire should also already be plugged into one of the lead electrodes in the black dot (GND).

• Reference: You will need to plug the left and right ear reference electrodes into the appropriate white dot (VIN-) inputs on the L and R electrode leads. Make sure that the left ear electrode is plugged into the left electrode lead (T3) and the right ear electrode is in the right electrode lead (T4).

F7

GND

FP1

FP2

Data Collection

You will use NEURO9 as the recording computer. Once you have set-up the EEG

cap and electrode connections you can start the BIOPAC recording program. We will not be using a lesson template as usual for this experiment! • Double Click PSY230-EEG on the desktop and the program will open. • Click on start to beginning recording and check the signal on the screen. • A message will pop up saying “The file unititled0000.acq already exists.” Click

Overwrite. The signal on the screen should have variability in both left and right channels. It is important that the subject be lying on the bed and be very still as any movement during the recording will introduce artificial noise into the signal. The top two channels of the image below shows an incorrect signal for the red channel (noisy) and a correct signal for the blue channel. The sine-wave signal show in the red channel indicates that the electrode on the left side was not making good contact with the scalp.

****If you do not have a good signal, then you need to make sure that the EEG electrodes are making good contact with the scalp, that you have filled the electrodes with the appropriate amount of gel, and that the ear reference electrodes are properly in place. You may need to adjust the tightness of the strap that holds the electrodes in place.****

Incorrect Left (Red)

Correct Right (Blue)

The above image has both correct signals for the red and the blue channels. This is the type of signal that you want to see before you actually start your recording. If you don’t have this type of signal do not proceed with the test as your data will be meaningless and you will have to re-do the lab. Start Recording:

• Once, you are happy with the quality of the signal, you can open the stimulus file on the desktop of the NEURO10 computer (PSY230-EEG) and insert a marker on the BIOPAC to indicate that you have started recording.

• The stimulus will begin playing automatically when the CoolEdit program opens. • Insert markers at the start of each stimulus and baseline segment. • Make sure that you label the marker with either: Baseline, Music, or Language

depending on the stimulus. When you finish recording you MUST SAVE YOUR DATA IN THE CORRECT PLACE. BIOPAC will NOT automatically save your data so make sure to save your file. Go to File – Save As and Save in the Psy230 Folder on the Desktop. Carefully disconnect the ear electrodes and EEG cap and wash the electrode gel out of the ear electrodes and the inside of the EEG T3 and T4 electrodes with the Ivory soap and Q-Tips in the lab. Also be sure to put extra gel back in and rinse out the syringe. Then, re-hook up the connections back in the biofeedback room.

Correct Left (Red)

Correct Right (Blue)

Data Analysis Opening the data:

• The BIOPAC needs to be connected and on • Double click on the BioPac BSL 4.0 MP 36 Icon • Click on the Pro tab and open any random lesson (such as H01) • Go to File – Open and retrieve your data file from the folder on the Desktop.

What you will see: There are 6 data channels shown on the screen for your EEG recording. The top two channels are the raw recordings from the left (T3, red) and right (T4, blue) electrodes. The other 4 channels are the beta wave components from the raw data signals. There is a duplicate channel for each electrode (left, T3, aqua & black; right, T4, pink & red). You will measure the activity in the raw beta wave channels for the aqua (left) and pink (right) channels. Integrating the Channels: You need to convert the bottom 2 duplicate channels (black and red) into an integrated response in order to measure total activation. To integrate the channels:

• first click on the left-hand channel label in order to select the black channel. In the figure below, the black channel has been selected as shown by the blue highlight.

Raw Left (T3)

Beta Left (T3)

Raw Right (T4)

Beta Right (T4) Beta Left (T3)

Beta Right (T4)

• Then choose, Transform à Integrate. • Choose the option: average over samples and put 30 as the number of samples

o Select RMS o Check the box that says “Transform Entire Wave”

• Next select the bottom, red waveform and repeat the process to integrate this channel. Once you have integrated your channels save your data as another file so that if you have problems you can return to your original file prior to integration.

Recording Data: Set-up the measurement box in the following configuration:

Channel 40: Stddev Channel 41: Stddev Channel 42: Area Channel 43: Area SC: Delta T

• Using your Delta T box, select 20 s of each baseline and stimulus and enter the standard deviation and area values into the data analysis EXCEL sheet available for download from the course website.

• Be sure to carefully enter your values into the correct cells in the worksheet. The worksheet is set-up to calculate the percent change response (stimulus divided by baseline) for each of the measurements.

After you have entered all of your data into the individual sheet to calculate your percent change from baseline, you must copy and paste the RESPONSE values into the appropriate STDEV and AREA sheets on GOOGLE DOCS using the links on the course laboratory website.

ALL DATA MUST BE COLLECTED, ANALYZED, AND ENTERED INTO THE GROUP DATA EXCEL SHEET ON GOOGLE DOCS NO LATER THAN THE

DEADLINE LISTED ON THE COURSE WEBSITE.

ANYONE FAILING TO ENTER THEIR INDIVIDUAL DATA INTO THE GROUP SHEET BY THIS TIME WILL RECEIVE A 10% DEDUCTION FROM THEIR FINAL

LAB REPORT GRADE.