It is important that before each session, you record (or verify previous settings) the scalp locations where data is being recorded/trained. This helps to keep training records clear and is an extra step that is necessary to ensure you can compare the data recorded at each site appropriately later.
After creating the Player and Configuring your EEG amplifier, click on “Exercise Menu, then “Core Clinician Screens,” and “Sensor Placement” which opens the Player Information dialog box.
The Sensor Placement screen will appear. In the upper left is a Spectrogram, an Oscilloscope on the bottom left (both display the selected channel specified on the Dropdown menu below the Spectrogram) and most of the right side of the screen shows a representation of various 10-20 Scalp locations for sensor placement. your EEG amplifier, click on “Exercise Menu, then “Core Clinician Screens,” and “Sensor Placement” which opens the Player Information dialog box.
To record a placement, find the location and click with the left mouse button on the desired location. A new menu will appear. From this new screen, click on the desired Channel and press OK to select that location at that Channel.
Note that only the number of channels available for your configured device will be available for selection BUT you do not need to assign ALL of the available channels.
You can also use the drop-down menu at the bottom to assign a color to each channel. This may be useful to match sensor locations with sensor cable colors.
Continue assigning Channels until you have recorded all of the channels that you will be using during that day’s training protocol. Do NOT assign additional channels if you do not intend to use them during training nor should you skip channels if at all possible.
There are five additional “Custom” sensor locations available at the bottom of the screen if you are using a site that is not represented on the default map.
Nasion to Inion Measurement
The instructions on the next few pages will serve as a basic tutorial in locating some of the more common locations used in EEG Training and in finding the three reference distances used to find the remaining locations. Those reference measurements are:
- The distance from the Nasion to the Inion along the midline of the scalp.
- The distance between the two preauricular points.
- The circumference measurement of the head.
Follow the instructions below to begin the measurement for the Nasion to Inion measurement.
- Find the Nasion and Inion. The Nasion is the indentation between the nose and the forehead. The Inion is the peak of the knob or ridge that can be felt as you run your finger up the back of the neck to the skull. You have to measure from the peak of the inion not the valley below it.
- Measure using centimeter side of tape measure between Nasion and Inion down the central line of head. Mark down this distance.
- 10 % of the total distance up from Nasion is Fpz. Mark this spot.
- 10% of the total distance up from Inion is Oz. Mark this spot.
- On the central line 50% between Nasion and Inion is Cz. Mark this spot.
Cz and Fpz are sites that are fairly commonly used in EEG research and training protocols. Those two sites and Oz are also used as reference points for next steps, 2 and 3.
A1 to A2 (Preauricular) Measurement
After finding the Nasion to Inion measurement in Step 1, the next step is measuring the distance from the left to the right lateral sides of the scalp. This is done by measuring from A1 to A2 and passing through the site Cz which was located in Step 1. Follow the instructions below:
- Find the preauricular points, A1 and A2. The Preauricular points are the indentations above the cartilage that covers the external ear opening and are found on both the left and right sides.
- Measure using centimeter side of tape measure between A1 and A2 over the crown of the head. This measurement should go through the previously marked Cz location. Mark down this distance.
- 10 % of the total distance up from A1 is T3. Mark this spot.
- 10% of the total distance up from A2 is T4. Mark this spot.
- On the central line 50% between A1 and A2 is Cz. Mark this spot. This should be fairly close to the spot for Cz marked in Step 1. A common mistake is to take the tape to far towards the
A common mistake with this measurement occurs when the measuring tape “drifts” to far towards the front of the head or the rear of the head. Be careful to go over the crown of the head which should pass very close to the site you marked as Cz in Step 1. This will also serve as a verification of the original measurement for Cz. If you find that the original mark for Cz and the 50% measurement from A1 to A2 don’t line up fairly closely, this could be an indication that either the measurement in step 1 was wrong or your alignment in Step 2 is off.
The sites of T3 and T4 are used in Step 3 to help measurement the circumference measurement of the scalp.
Circumference Measurement
To find the circumference measurement, you will use as reference points, the sites of Fpz and Oz (measured in Step 1) and T3 and T4 (measured in Step 2).
- Using the centimeter side of the measurement tape, measure around the circumference of the head being sure to go through the previously marked spots Fpz, T3, Oz, & T4. Record this distance.
- The circumference measurement will be used to locate the other sites located along the circumference such as F7, T5 or Fp1 and Fp2.
Finding MidPoints
You can now use the 3 measures,
- Nasion to Inion (Step 1)
- Preauricular A1 to A2 (Step 2)
- Circumference measure (Step 3)
and the reference points
- Fpz, T3, Oz, T4 and Cz (highlighted in red in image at left)
and Percentages of distances on the various axes to find any point on the head using the 10-20 system. Any point not on one of the three main axes is usually located by finding a point on each of two axis and finding a midpoint between those locations. These sites are represented on the image to the right by the designation “1/2” and dotted green lines between two main axis locations to indicate those locations can be found by finding the midpoint between the two main axis sites. For example, F3 (left front scalp) is located halfway between the locations F7 and Fz.
More Examples
To find the site location for F7 which is 15% of the circumference measurement (highlighted in the image below) back from Fpz on the left side of the scalp on the Circumference measurement.
1. Measure the Nasion to Inion measurement and then mark the points for Fpz and Oz
2. Measure the A1 – A2 measurement and then mark the points for T3 and T4.
3. You would now need to do the circumference measurement. Your measuring tape should pass through the points marked for FPz, Oz, T3, and T4 to insure you have the tape at the proper level on the head.
4. Once you have the Circumference measurement, you can start at Fpz and measure around the left of the scalp towards Oz by 15% of the circumference. That point will be F7.
For a much more complicated location, let’s try to locate Tp3 which is a non-standard 10-20 measurement. TP3 is 50% between T3 and P3. P3 is 50% between Pz and T5.
1. Measure the Nasion to Inion measurement and then mark the points for Fpz and Oz. Also mark 30% from Inion towards the front of the scalp. Mark this point which is Pz.
2. Measure the A1 – A2 measurement and then mark the points for T3 and T4.
3. You would now need to do the circumference measurement. Your measuring tape should pass through the points marked for FPz, Oz, T3, and T4 to ensure you have the tape at the proper level on the head.
4. Once you have the Circumference measurement, you can start at T3 and measure back towards Oz by 10% of the circumference measurement. This point is T5.
5. Place the measuring tape with one end at T5 and one end at Pz. Measure halfway between those points and make a mark. This mark is P3.
6. Place the measuring tape with one end at T3 and one end at P3. Measure halfway between those points and make a mark. This mark is TP3.
