The Neurophysiological Biomarker Toolbox (NBT)


Table of Contents

Mounting the EEG-net

(This tutorial is for the EGI EEG setup at the Center for Neurogenomics and Cognitive Research, VU University Amsterdam)

  1. Check whether there is enough cling foil.
  2. The electrode nets conduct the electrical potentials from the scalp through little sponges that need to be soaked in a salty solution, called the electrolyte. To make the electrolyte, add 1 spoon of shampoo and 1 spoon of potassium chloride (KCl) to 1 liter of warm water (use the provided plastic spoons and bucket from the lab).
  3. Have the subject sit in a chair and measure the subject’s head circumference. Our lab has electrode nets for circumferences of 54-56 cm, 56-58 cm and 58-61 cm. Put a fitting EEG-net in the electrolyte solution and set a timer to 10 minutes.

    Meanwhile you can do the following:

  4. Ask the subject to wash his hair, and dry it. A clean hair improves electrode contact.
  5. Put a towel around the subject's neck/shoulders.
  6. Determine the location of the central electrode (Cz): 50% of the distance nasion-inion, 50% of the distance ear-ear, and mark this spot with the red marker (Figure 4).

    After 10 minutes:

  7. Take out the EEG-net. It is OK if the floor gets wet, but keep the connector at the end of the net free of electrolyte.
  8. Ask the subject to hold the EEG connector.
  9. Ask the subject to close his/her eyes and bend his/her head forward, gently apply the EEG-net from the back of the head to the front, while standing in front of the subject. Make sure that the Cz electrode is on top of the marked spot and that the Fz and Oz electrodes (numbers 11 and 75 for the 129-electrode net) are aligned in the sagittal plane. Adjusting the net while around the subject's head should only be done in one direction at a time and very gently (You should always move several electrodes together, it reduces the risk of breaking the electrodes.). Do not rotate the net. Re-apply the net if it is impossible to adjust safely.

    Figure 4 Basic skull anatomy and landmark electrode locations
    according to the 10-20 system


  10. Check to see if there are no electrodes up-side-down (the ones near the subject's neck tend to be) or are clearly not making good contact with the skin of the subject.
  11. Ask if the subject is comfortable.
  12. Insert the connector in the socket at the end of the arm that is mounted on the wall; there is a pin on one side of the connector: make sure it's on the left. Take care not to bend the pins, or get them wet.

Continue to Measuring the impedances

References

Jasper, H.H. The ten twenty electrode system of the international federation. Electroencephalography and Clinical Neurophysiology 10, 371-375, 1958

tutorial/preparing_the_eeg-net.txt · Last modified: 2011/10/17 10:18 by Simon-Shlomo Poil
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