In the active EEG phase we observe brain activity while the participant completes simple tasks on a computer. When we think, our neurons communicate with each other by electrical signals. A small portion of these signals produced by the brain can be measured on the scalp. For the measurement of the electrical changes on the scalp we use an EEG (electroencephalography) cap, and this measurement is what helps us draw conclusions about what happens in the brain. The EEG cap consists of small electrodes covered with sponges. We soak the cap (the sponges) in some slightly salty, warm water. These electrodes underneath the soaked sponges can measure the small electrical changes on the scalp very well. The method is completely non-invasive, the participant is merely wearing the EEG cap and is sitting in a comfortable chair while completing the tasks. This type of brain activity measurement is often conducted on babies as well.
The picture below shows that when an image appears on the screen, brain activity changes within just 100 milliseconds (1/10th of a second). In other words, in a 100 milliseconds the reaction to the image can already be detected.
The event-related potential measurements can have some really exciting results in adolescent children. The brain goes through a variety of changes in this age, and the event-related potential and other brain activity research provides us important information about brain development.