Part 2: EEG Net Application
Last updated
Last updated
Inform the subject what to expect. Before you do anything, give the participant a rundown of what is about to happen. It’s often helpful to show them the net.
“Before I apply the net, I’m going to find the center point of your scalp and mark it using this cosmetic crayon. Just an FYI, the net is a bit wet. It’s just water with a pinch of electrolytes and a drop of non-soap baby shampoo. That has the double effect of making your hair smell nice and it conducts your brain waves better. When I initially apply the net, it may feel a little awkward or uncomfortable until we shift it around to an optimal position. If any point you find the discomfort to be too overwhelming, don’t hesitate to speak up. We can move things around or take it off entirely.”
Find the midpoint of the participant’s top of head.
Measure the distance from the nasion (front) to the inion (back) to determine the halfway point in cm. Draw a line perpendicularly to the measuring band’s orientation.
Measure the distance from the left tragus to the right ear tragus (the cartilage that covers your earhole when you push it down) and determine the halfway point in cm.
Draw a line perpendicularly to the measuring band’s orientation.
Both lines should intersect with each other, making a small crosshair or plus on the center of their head. This point will serve as our alignment reference electrode Cz.
Place a towel around the participant's shoulders to avoid dripping onto their clothing.
Give the net's connector end to the participant to hold.
Open all chin straps on the net as much as possible.
Experimenter 1: Expand your hands inside of the front of the net with your palms facing away from you, and the net rests on the backside of your hands. Position yourself in front of the participant.
Experimenter 2: Expand your hands inside of the back of the net with your palms facing away from you, and the net rests on the backside of your hands. Position yourself behind the participant.
Both experimenters: Raise your arms over the participant to position the net above and behind their head. Bring the net down with your hands spread as wide as possible. Align the position of the reference Cz electrode to the midpoint you previously drew. Stretch the back of the net down around the skull.
Do not remove your hands until the reference electrode is aligned and the net is fully stretched down and around all sides of the skull.
Check in with the participant. If there is something pertinently bothering them, attend to that first.
Talk to the participant. Any movement of the net, their hair, their ears, etc. should be communicated.
Even if it’s against your nature, chat with them. Do not fall silent! Talking not only relaxes the patient in an otherwise awkward setup situation, but it also prompts them to communicate with you even if it’s against their nature to do so. Some folks are more hesitant to speak up when something’s pinching, which is exacerbated by you being shy.
Gently tighten the chin straps of net. This will help with the net's positioning on their face.
Make small lifts and shifts.
Weave your fingers in the between the electrodes of the area in question. Gently lift the net a few centimeters and shift it in the desired direction. You will want to do this if the black “Cz” electrode isn’t aligned with the scalp center point.
Pulling or yanking is both ineffective and potentially damaging to the net and participant. Don’t pull or yank.
Make sure the sponge surface of all electrodes are making contact with the skull.
