The cells that make up our bodies use electrical signals to send messages to each other. That’s why from the moment we’re born (even when we are sleeping) our brains are producing a small amount of electricity. This electricity can be measured using very sensitive recording tools – electrodes – that sit on the outside of the head and detect what is going on inside. Nothing goes into the head; we just measure the activity that comes out of the person’s brain. The electrodes sit on the surface of the hair in something like a swimming cap, that is connected to a computer.
This is what it looks like when people wear the caps that measure the electricity in their brain. Can you see the electrodes on them? We sometimes also place a couple on your cheek so that the computer knows when you move your eyes.
The constant activity of the brain that is measured by the electrodes is called the electroencephalogram or EEG. Below is an example of what an EEG recording looks like. See all the different lines? Each one shows electrical activity measured from different parts of the scalp.
Even though these wavy lines look like a big mess, they can reveal a lot about how the brain works. We can use them to look at what is happening in the brain when people do specific things, such as recognizing a familiar face. If we look at what is happening in the EEG immediately after a face appears on the computer screen, then we can work out what electrical activity is related to that ‘event’. This activity is called the event related potential (or ERP). ERPs help us to identify the bits of the brain are important for different things, and exactly when each one plays their part. They are really cool because they help us to better understand what is going on inside peoples’ heads!
How is an EEG performed?
What is it like to take part your research project that involves collecting ERPs?
If you take part in one of our studies, you will come in to Birkbeck, which is in Bloomsbury, Central London. We have special rooms here to run our activities with children and adults. When you come in, you will play specially designed computer games that involve looking at faces presented on a screen and making judgments about them, such as “Is that Tom?” and “Are they happy?`’.Most people find these games pretty easy and enjoyable.
While you are playing our computer games, we will record your brain activity via an EEG cap connected to a computer. Like I mentioned before, this cap is a bit like a swimming cap, only with lots of cords coming out of the back of it.
Making our recordings doesn’t hurt at all, but in order to get a good connection between our electrodes and your head, we often put some salt-water gel in your hair. This ‘goop’ can get a little bit messy, so we have
everything needed to wash your hair when you finish, if you want to.
Fitting the cap may take about 30 minutes – during which time you can chat to us, read a book or watch a film. After the cap is fitted, playing the computer games should take between 30 – 40 minutes. Then we’ll take the cap off and wash your hair in our special hairdressing chair (if you want us to). Altogether a session takes a maximum of 3 hours.
