Putting on a net

Well, first things first. I will try to describe what ERP is very soon, but I am supposed to help Serena put on a net tomorrow and I wanted to write down what I know about putting on nets so far.

The net consists of electrodes. These electrodes are attached to the scalp at various locations. The recording locations are most often chosen according to the International 10-20 system. First of all there are different sizes of nets and we have to figure out which net should be used for a given participant. To figure that out, we measure the scalp circumference. This is basically done by measures the distance between the nasion (which is basically the point between you eyelashes or more formally the distinctly depressed area directly between the eyes, just superior to the bridge of the nose) and the inion (which basically refers to the protuberance on the rear-back of the skull), covering the ears. Depending on this distance, you choose a certain size of net.

Afterwards, to be able to place the net appropriately, you figure out somewhat the middle of the head, by first measuring the distance from nasion to inion and make a longitudinal line somewhere on the top of the head. You also measure the distance from medus to medus, pre-auricular points and make a latitudinal line on the top of the head. Divide this distance into two. ou then mark the intersection of these two lines. This middle point is where your central zero point electrode should go. But before putting on the net electrodes, or rather the whole net, should be soaked in a special solution to increase its conductance.

After the net is soaked according to the instructions written on the buckets, which I don't know right now, you then place the net on the subject's head. This is better be done in the experiment room. You put your hands in the net and place it on the subject's head trying to make the center correspond to the intersection you draw. Also, you should make sure that the reference electrodes (on the ears), the electrodes beneath the eyes, the nasion electrode are all properly placed!

Then you can connect the net to the computer and see how many of the electrodes have signal. Serena told me that one should not have a cluster of red dots in one location, but it's okay to have 5 electrodes that do not have signal. The important part if to get the reference electrodes definitely working! Once the net is placed and connected to the computer, you can then use a small pen-like this to wet more electrodes and try to make them work. Hopefully, tomorrow I will be able to do this successfully! :)

Wish me luck!