Rights: The University of Waikato, All rights reserved. Published 21 July 2007 Download

Dr Richard Jones from the Van der Veer Institute for Parkinson’s & Brain Research talks about how an EEG detects electrical activity from the 100 billion neurons in the brain.

When the neurons in the brain are firing signals, this electrical activity can be detected on the scalp using an electroencephalogram (EEG). Electrodes can be placed over the scalp in a particular arrangement that can measure these very small signals, which are fed into an amplifier and then analysed by a computer. A substance called collodion is used to help hold the electrodes in place.


This is the standard – it’s called the International 10/20 system for location of the electrodes and so it goes over various parts of the brain, so it’s a fairly standard placement. And this is 64 channels, but in fact you can get some EEG machines that are up to 256 channels, which is a lot of signals.

We’ve got the brain sort of firing all over the place with all these neurons in it, and there is all this electrical activity, and it comes to the scalp, and you get these certain patterns, these rhythms that we see, called EEG. They’re very small voltages, they’re about, sort of up to 100 microvolts, but we can measure them. So we put these electrodes on the scalp, put some collodion between them so that we get the conduction, and we then measure the electrical activity. This comes off down these cables, goes into an amplifier, amplifies the signals, and then we can put it into a computer to then analyse it on the screen.